ICONTOUR

The ICONTOUR procedure creates an iTool and associated user interface (UI) configured to display and manipulate contour data.

This routine is written in the IDL language. Its source code can be found in the file icontour.pro in the lib/itools subdirectory of the IDL distribution.

Using Palettes

Contour colors can be specified in several ways. By default, all contour levels are black. The COLOR keyword can be used to change the color of all contour levels. For example, you can change contour levels to red by setting COLOR = [255, 0, 0]. Individual color levels can be specified when the iContour tool is in palette color mode, which allows a color table to be used. You can activate the palette color mode from the IDL Command Line by setting either of the RGB_TABLE or RGB_INDICES keywords, or from the iContour tool's property sheet by changing the Use palette color setting to True.

If the iContour tool is in palette color mode, a colorbar can be inserted through the Insert menu. The colorbar displays a sample of the current palette associated with the contour display. The data values of the axis of the colorbar are based on the data range of the Z argument and the contour level values.

The minimum value of the colorbar axis represents the minimum of the data range. The maximum value of the axis is the greater of than the maximum of the data range and the highest contour level value.

Syntax

Arguments

A vector or two-dimensional array specifying the x-coordinates for the contour surface. If X is a vector, each element of X specifies the x-coordinate for a column of Z (e.g., X[0] specifies the x-coordinate for Z[0, *]). If X is a two-dimensional array, each element of X specifies the x-coordinate of the corresponding point in Z (i.e., X_ij specifies the x-coordinate for Z_ij).

A vector or two-dimensional array specifying the y-coordinates for the contour surface. If Y is a vector, each element of Y specifies the y-coordinate for a row of Z (e.g., Y[0] specifies the y-coordinate for Z[*,0]). If Y is a two-dimensional array, each element of Y specifies the y-coordinate of the corresponding point in Z (Y_ij specifies the y-coordinate for Z_ij).

A vector or two-dimensional array containing the values to be contoured. If the X and Y arguments are provided, the contour is plotted as a function of the (x, y) locations specified by their contents. Otherwise, the contour is generated as a function of the two-dimensional array index of each element of Z.

Keywords

AM_PM

Set this keyword to a vector of 2 strings indicating the names of the AM and PM strings when processing explicitly formatted dates (CAPA, CApA, and CapA format codes) with the LABEL_FORMAT keyword. See Format Codes for more information on format codes.

ANISOTROPY

Set this keyword equal to a three-element vector [x, y, z] that represents the multipliers to be applied to the internally computed correction factors along each axis that account for anisotropic geometry. Correcting for anisotropy is particularly important for the appropriate representations of downhill tickmarks.

By default, IDL will automatically compute correction factors for anisotropy based on the [XYZ] range of the contour geometry. If the geometry (as provided via the GEOMX, GEOMY, and GEOMZ keywords) falls within the range [xmin, ymin, zmin] to [xmax, ymax, zmax], then the default correction factors are computed as follows:

dx = xmax - xmin 
dy = ymax - ymin 
dz = zmax - zmin 
; Get the maximum of the ranges: 
maxRange = (dx > dy) > dz  
IF (dx EQ 0) THEN xcorrection = 1.0 ELSE $ 
   xcorrection = maxRange / dx 
IF (dy EQ 0) THEN ycorrection = 1.0 ELSE $ 
   ycorrection = maxRange / dy 
IF (dz EQ 0) THEN zcorrection = 1.0 ELSE $ 
   zcorrection = maxRange / dz

This internally computed correction is then multiplied by the corresponding [x, y, z] values of the ANISOTROPY keyword. The default value for this keyword is [1,1,1]. IDL converts, maintains, and returns this data as double-precision floating-point.

BACKGROUND_COLOR

Set this keyword to an RGB value specifying the color to be used as the background color for the view. The default is [255, 255, 255] (white). The BACKGROUND_COLOR keyword can be used when a tool is being created or when a new visualization is being created in an existing tool with the use of the OVERPLOT, VIEW_NUMBER or VIEW_NEXT keywords. The background color is applied to the current view. For example, if multiple views have been created with the VIEW_GRID keyword, and the VIEW_NUMBER keyword is used to create a visualization in the second view, use of the BACKGROUND_COLOR keyword would set the background color in the second view only.

C_COLOR

Set this keyword to a 3 by N array of RGB colors representing the colors to be applied at each contour level. If there are more contour levels than elements in this vector, the colors will be cyclically repeated. If C_COLOR is set to 0, all contour levels will be drawn in the color specified by the COLOR keyword (this is the default).

However, the C_COLOR keyword does not activate the palette color mode, which is recommended when working with contour levels and color. This mode can be activated with the RGB_INDICES and RGB_TABLE keywords. See Using Palettes for more details.

C_FILL_PATTERN

Set this keyword to an array of IDLgrPattern objects representing the patterns to be applied at each contour level if the FILL keyword is non-zero. If there are more contour levels than fill patterns, the patterns will be cyclically repeated. If this keyword is set to 0, all contour levels are filled with a solid color (this is the default).

C_LABEL_INTERVAL

Set this keyword to a vector of values indicating the distance (measured parametrically relative to the length of each contour path) between labels for each contour level. If the number of contour levels exceeds the number of provided intervals, the C_LABEL_INTERVAL values will be repeated cyclically. The default is 0.4.

C_LABEL_NOGAPS

Set this keyword to a vector of values indicating whether gaps should be computed for the labels at the corresponding contour value. A zero value indicates that gaps will be computed for labels at that contour value; a non-zero value indicates that no gaps will be computed for labels at that contour value. If the number of contour levels exceeds the number of elements in this vector, the C_LABEL_NOGAPS values will be repeated cyclically. By default, gaps for the labels are computed for all levels (so that a contour line does not pass through the label).

C_LABEL_OBJECTS

Set this keyword to an array of object references to provide examples of labels to be drawn for each contour level. The objects specified via this keyword must inherit from one of the following classes:

IDLgrSymbol

IDLgrText

If a single object is provided, and it is an IDLgrText object, each of its strings will correspond to a contour level. If a vector of objects is used, any IDLgrText objects should have only a single string; each object will correspond to a contour level.

By default, with C_LABEL_OBJECTS set equal to a null object, IDL computes text labels that are the string representations of the corresponding contour level values.

The contour labels will have the same color as their contour level (see C_COLOR) unless the C_USE_LABEL_COLOR keyword is specified. The orientation of the label will be automatically computed unless the C_USE_LABEL_ORIENTATION keyword is specified. The horizontal and vertical alignment of any text labels will default to 0.5 (i.e., centered) unless the USE_TEXT_ALIGNMENTS keyword is specified.

C_LABEL_SHOW

Set this keyword to a vector of integers. For each contour value, if the corresponding value in the C_LABEL_SHOW vector is non-zero, the contour line for that contour value will be labeled. If the number of contour levels exceeds the number of elements in this vector, the C_LABEL_SHOW values will be repeated cyclically. The default is 0 indicating that no contour levels will be labeled.

C_LINESTYLE

Set this keyword to an array of linestyles representing the linestyles to be applied at each contour level. The array may be either a vector of integers representing pre-defined linestyles, or an array of 2-element vectors representing a stippling pattern specification. If there are more contour levels than linestyles, the linestyles will be cyclically repeated. If this keyword is set to 0, all levels are drawn as solid lines (this is the default).

To use a pre-defined line style, set the C_LINESTYLE property equal to one of the following integer values:

0 = Solid line (the default)

1 = dotted

2 = dashed

3 = dash dot

4 = dash dot dot dot

5 = long dash

6 = no line drawn

To define your own stippling pattern, specify a two-element vector [repeat, bitmask], where repeat indicates the number of times consecutive runs of 1's or 0's in the bitmask should be repeated. (That is, if three consecutive 0's appear in the bitmask and the value of repeat is 2, then the line that is drawn will have six consecutive bits turned off.) The value of repeat must be in the range 1 £ repeat £ 255.

The bitmask indicates which pixels are drawn and which are not along the length of the line. Bitmask is most conveniently specified as a 16-bit hexadecimal value.

For example, LINESTYLE = [2, 'F0F0'X] describes a dashed line (8 bits on, 8 bits off, 8 bits on, 8 bits off).

C_THICK

Set this keyword to an array of line thicknesses representing the thickness to be applied at each contour level, where each element is a value between 1.0 and 10.0 points. If there are more contour levels than line thicknesses, the thicknesses will be cyclically repeated. If this keyword is set to 0, all contour levels are drawn with a line thickness of 1.0 points (this is the default).

C_USE_LABEL_COLOR

Set this keyword to a vector of values (0 or 1) to indicate whether the COLOR property value for each of the label objects (for the corresponding contour level) is to be used to draw that label. If the number of contour levels exceeds the number of elements in this vector, the C_USE_LABEL_COLOR values will be repeated cyclically. By default, this value is zero, indicating that the COLOR properties of the label objects will be ignored, and the C_COLOR property for the contour object will be used instead.

C_USE_LABEL_ORIENTATION

Set this keyword to a vector of values (0 or 1) to indicate whether the orientation for each of the label objects (for the corresponding contour level) is to be used when drawing the label. For text, the orientation of the object corresponds to the BASELINE and UPDIR property values; for a symbol, this refers to the default (un-rotated) orientation of the symbol. If the number of contour levels exceeds the number of elements in this vector, the C_USE_LABEL_ORIENTATION values will be repeated cyclically. By default, this value is zero, indicating that orientation of the label object(s) will be set to automatically computed values (to correspond to the direction of the contour paths).

C_VALUE

Set this keyword to a scalar value or a vector of values for which contour values are to be drawn. If this keyword is set to 0, contour levels will be evenly sampled across the range of the Z argument, using the value of the N_LEVELS keyword to determine the number of samples. IDL converts, maintains, and returns this data as double-precision floating-point.

CLIP_PLANES

Set this keyword to an array of dimensions [4, N] specifying the coefficients of the clipping planes to be applied to this object. The four coefficients for each clipping plane are of the form [A, B, C, D], where Ax + By + Cz + D = 0. Portions of this object that fall in the half space Ax + By + Cz + D > 0 will be clipped. By default, the value of this keyword is a scalar (-1) indicating that no clipping planes are to be applied.

COLOR

Set this keyword to the color to be used to draw the contours. This color is specified as an RGB vector. The default is [0, 0, 0]. This value will be ignored if the C_COLOR keyword is set to a vector.

DAYS_OF_WEEK

Set this keyword to a vector of 7 strings to indicate the names to be used for the days of the week when processing explicitly formatted dates (CDWA, CDwA, and CdwA format codes) with the LABEL_FORMAT keyword. See Format Codes for more information on format codes.

DEPTH_OFFSET

Set this keyword to an integer value that specifies an offset in depth to be used when rendering filled primitives. This offset is applied along the viewing axis, with positive values moving the primitive away from the viewer.

The units are "Z-Buffer units," where a value of 1 is used to specify a distance that corresponds to a single step in the device's Z-Buffer.

Use DEPTH_OFFSET to always cause a filled primitive to be rendered slightly deeper than other primitives, independent of model transforms. This is useful for avoiding stitching artifacts caused by rendering lines or polygons on top of other polygons at the same depth.

DIMENSIONS

Set this keyword to a two-element vector of the form [width, height] to specify the dimensions of the drawing area of the specific tool in units specified by the UNITS keyword. If no value is provided, a default value of one half the screen size is used. The minimum width of the window correlates to the width of the menubar. The minimum window height is 100 pixels.

DOWNHILL

Set this keyword to indicate that downhill tick marks should be rendered as part of each contour level to indicate the downhill direction relative to the contour line.

FILL

Set this keyword to indicate that the contours should be filled. The default is to draw the contour levels as lines without filling. Filling contours may produce less than satisfactory results if your data contains NaNs, or if the contours are not closed.

GRID_UNITS

Set this keyword to an integer specifying the units for the contour grid. This keyword applies only when there is a map projection inserted. It has the following values:

0 - None. The contour grid is in arbitrary units that are not tied to a map projection. The contour will not be warped to the current map projection.

1 - Meters. The contour grid is in meters, and is tied to a particular map projection. The contour will be automatically warped to the current map projection. You are responsible for choosing the dataspace map projection that matches the contour's map projection.

2 - Degrees. The contour grid is in degrees longitude/latitude, and will be automatically warped to the current map projection.

HIDE

Set this keyword to a boolean value to indicate whether this object should be drawn:

0 = Draw graphic (the default)

1 = Do not draw graphic

IDENTIFIER

Set this keyword to a named variable that will contain the iToolID for the created tool. This value can then be used to reference this tool during overplotting operations or command-line-based tool management operations.

LABEL_FONT

Set this keyword to an instance of an IDLgrFont object to describe the default font to be used for contour labels. This font will be used for all text labels automatically generated by IDL (i.e., if C_LABEL_SHOW is set but the corresponding C_LABEL_OBJECTS text object is not provided), or for any text label objects provided via C_LABEL_OBJECTS that do not already have the font property set. The default value for this keyword is a NULL object reference, indicating that 12 pt. Helvetica will be used.

LABEL_FORMAT

Set this keyword to a string that represents a format string or the name of a function to be used to format the contour labels. If the string begins with an open parenthesis, it is treated as a standard format string. (Refer to the Format Codes in the IDL Reference Guide.) If the string does not begin with an open parenthesis, it is interpreted as the name of a callback function to be used to generate contour level labels.

The callback function is called with three parameters: Axis, Index, and Value and an optional DATA keyword, where:

Axis is simply the value 2 to indicate that values along the Z axis are being formatted, which allows a single callback routine to be used for both axis labeling and contour labeling.

Index is the contour level index (indices start at 0).

Value is the data value of the current contour level.

DATA is the optional keyword allowing any user-defined value specified through the LABEL_FRMTDATA keyword to ICONTOUR.

LABEL_FRMTDATA

Set this keyword to a value of any type. It will be passed via the DATA keyword to the user-supplied formatting function specified via the LABEL_FORMAT keyword, if any. By default, this value is 0, indicating that the DATA keyword will not be set (and furthermore, need not be supported by the user-supplied function).

LABEL_UNITS

Set this keyword to a string indicating the units to be used for default contour level labeling.

"Numeric"

"Years"

"Months"

"Days"

"Hours"

"Minutes"

"Seconds"

"Time" - Use this value to indicate that the contour levels correspond to time values; IDL will determine the appropriate label format based upon the range of values covered by the contour Z data.

"" - The empty string is equivalent to the "Numeric" unit. This is the default.

If any of the time units are utilized, then the contour values are interpreted as Julian date/time values.

LOCATION

Set this keyword to a two-element vector of the form [x, y] to specify the location of the upper left-hand corner of the tool relative to the display screen, in units specified by the UNITS keyword.

MACRO_NAMES

Set this keyword to a scalar string or an array of strings that specifies the names of one or more macros to run. The macro names are retrieved and the macros are run sequentially after the iTool and (if applicable) any visualizations have been created. If a macro of the specified name does not exist, IDL generates an error and the routine exits.

MAX_VALUE

Set this keyword to the maximum value to be plotted. Data values greater than this value are treated as missing data. The default is the maximum value of the input Z data. IDL converts, maintains, and returns this data as double-precision floating-point.

MONTHS

Set this keyword to a vector of 12 strings indicating the names to be used for the months when processing explicitly formatted dates (CMOA, CMoA, and CmoA format codes) with the C_LABEL_FORMAT keyword. See Format Codes for more information on format codes.

MIN_VALUE

Set this keyword to the minimum value to be plotted. Data values less than this value are treated as missing data. The default is the minimum value of the input Z data. IDL converts, maintains, and returns this data as double-precision floating-point.

NAME

NO_SAVEPROMPT

Set this keyword to cause the iTool not to prompt the user to save changes when closing the tool. The default is to prompt the user to save changes.

N_LEVELS

Set this keyword to the number of contour levels to generate. This keyword is ignored if the C_VALUE keyword is set to a vector, in which case, the number of levels is derived from the number of elements in that vector. Set this keyword to zero to indicate that IDL should compute a default number of levels based on the range of data values. This is the default.

OVERPLOT

Set this keyword to an iToolID to direct the graphical output of the particular tool to the tool specified by the provided iToolID.

Set this keyword to 1 (one) to place the graphical output for the command in the current tool. If no current tool exists, a new tool is created.

PLANAR

Set this keyword to indicate that the contoured data is to be projected onto a plane. Unlike the underlying IDLgrContour object, the default for ICONTOUR is planar (PLANAR = 1), which displays the contoured data in a plane. See the ZVALUE keyword to specify the Z value at which to display the planar Contour plot if it is displayed in a three dimensional data space.

RGB_INDICES

Set this keyword to a vector of indices into the color table to select colors to use for contour level colors. Setting the RGB_INDICES keyword activates the palette color mode, which allows colors from a specified color table to be used for the contour levels. The values set for RGB_INDICES are indices into the RGB_TABLE array of colors. If the number of colors selected using RGB_INDICES is less than the number of contour levels, the colors are repeated cyclically. If indices are not specified with the RGB_INDICES keyword, a default vector is constructed based on the values of the contour levels within the contour data range scaled to the byte range of RGB_TABLE.

RGB_TABLE

Set this keyword to either a 3 by 256 or 256 by 3 array containing color values to use for contour level colors. Setting the RGB_TABLE keyword activates the palette color mode, which allows colors from a specified color table to be used for the contour levels. The colors for each level are selected from RGB_TABLE using the RGB_INDICES vector. If indices are not specified with the RGB_INDICES keyword then a default vector is constructed based on the values of the contour levels within the contour data range scaled to the byte range of RGB_TABLE.

If the visualization is in palette color mode, but colors have not been specified with the RGB_TABLE keyword, the contour plot uses a default grayscale ramp.

SHADE_RANGE

Set this keyword to a two-element array that specifies the range of pixel values (color indices) to use for shading. The first element is the color index for the darkest pixel. The second element is the color index for the brightest pixel. This value is ignored when the contour is drawn to a graphics destination that uses the RGB color model.

SHADING

0 = Flat (default): The color has a constant intensity for each face of the contour, based on the normal vector.

1 = Gouraud: The colors are interpolated between vertices, and then along scanlines from each of the edge intensities.

Gouraud shading may be slower than flat shading, but results in a smoother appearance.

STYLE_NAME

Set this keyword equal to a string that specifies the name of a user-defined or a system style. If a style of the specified name does not exist, IDL generates an error and the routine exits. The style is applied using the following rules:

If the tool exists and /OVERPLOT is specified, then the style is only applied to the newly-created visualizations within the current view. The current tool style is not updated with the new style, nor is the style applied to any other items within the view.

Otherwise, if the tool exists and either VIEW_NEXT or VIEW_NUMBER is being used to select a different view, then the style is applied to all items within that view. The current tool style is updated with the new style.

Otherwise, if a new tool is being created, then the style is applied to all items within all views. The current tool style is updated with the new style.

TICKINTERVAL

Set this keyword equal to a number indicating the distance between downhill tickmarks, in data units. If TICKINTERVAL is not set, or if you explicitly set it to zero, IDL will compute the distance based on the geometry of the contour. IDL converts, maintains, and returns this data as double-precision floating-point.

TICKLEN

Set this keyword equal to a number indicating the length of the downhill tickmarks, in data units. If TICKLEN is not set, or if you explicitly set it to zero, IDL will compute the length based on the geometry of the contour. IDL converts, maintains, and returns this data as double-precision floating-point

TITLE

Set this keyword to a string to specify a title for the tool. The title is displayed in the title bar of the tool and is used for tool-related display purposes only - as the root of the hierarchy shown in the Tool Browser, for example.

USE_TEXT_ALIGNMENTS

Set this keyword to indicate that, for any IDLgrText labels (as specified via the C_LABEL_OBJECTS keyword), the ALIGNMENT and VERTICAL_ALIGNMENT property values for the given IDLgrText object(s) are to be used to draw the corresponding labels. By default, this value is zero, indicating that the ALIGNMENT and VERTICAL_ALIGNMENT properties of the label IDLgrText object(s) will be set to default values (0.5 for each, indicating centered labels).

VIEW_GRID

Set this keyword to a two-element vector of the form [columns, rows] to specify the view layout within the new tool. This keyword is only used if a new tool is being created (for example, if OVERPLOT, VIEW_NEXT, or VIEW_NUMBER are specified then VIEW_GRID is ignored).

VIEW_NEXT

Set this keyword to change the view selection to the next view following the currently-selected view before issuing any graphical commands. If the currently-selected view is the last one in the layout, then /VIEW_NEXT will cause the first view in the layout to become selected. This keyword is ignored if no current tool exists.

VIEW_NUMBER

Set this keyword to change the currently-selected view to the view specified by the VIEW_NUMBER before issuing any graphical commands. The view number starts at 1, and corresponds to the position of the view within the graphics container (not necessarily the position on the screen). This keyword is ignored if no current tool exists.

[XYZ]GRIDSTYLE

The index of the linestyle to be used for plot tickmarks and grids (i.e., when [XYZ]TICKLEN is set to 1.0). See LINESTYLE for a list of linestyles.

[XYZ]MAJOR

Set this keyword to an integer representing the number of major tick marks. The default is -1, specifying that IDL will compute the number of tickmarks. Setting MAJOR equal to zero suppresses major tickmarks entirely. ZMAJOR is ignored unless PLANAR is set to 0.

[XYZ]MINOR

Set this keyword to an integer representing the number of minor tick marks. The default is -1, specifying that IDL will compute the number of tickmarks. Setting MINOR equal to zero suppresses minor tickmarks entirely. ZMINOR is ignored unless PLANAR is set to 0.

[XYZ]RANGE

Set this keyword to the desired data range of the axis, a 2-element vector. The first element is the axis minimum, and the second is the maximum. ZRANGE is ignored unless PLANAR is set to 0.

[XYZ]SUBTICKLEN

Set this keyword to a floating-point scale ratio specifying the length of minor tick marks relative to the length of major tick marks. The default is 0.5, specifying that the minor tick mark is one-half the length of the major tick mark. ZSUBTICKLEN is ignored unless PLANAR is set to 0.

[XYZ]TEXT_COLOR

Set this keyword to an RGB value specifying the color for the axis text. The default value is [0, 0, 0] (black). ZTEXT_COLOR is ignored unless PLANAR is set to 0.

[XYZ]TICKFONT_INDEX

Set this keyword equal to one of the following integers, which represent the type of font to be used for the axis text:

0 = Helvetica

1 = Courier

2 = Times

3 = Symbol

4 = Hershey

[XYZ]TICKFONT_SIZE

Set this keyword to an integer representing the point size of the font used for the axis text. The default is 12.0 points. ZTICKFONT_SIZE is ignored unless PLANAR is set to 0.

[XYZ]TICKFONT_STYLE

Set this keyword equal to one of the following integers, which represent the style of font to be used for the axis text:

0 = Normal

1 = Bold

2 = Italic

3 = Bold Italic

[XYZ]TICKFORMAT

Set this keyword to a string, or an array of strings, in which each string represents a format string or the name of a function to be used to format the tick mark labels. If an array is provided, each string corresponds to a level of the axis. The TICKUNITS keyword determines the number of levels for an axis.

If the string begins with an open parenthesis, it is treated as a standard format string. See Format Codes.

If the string does not begin with an open parenthesis, it is interpreted as the name of a callback function to be used to generate tick mark labels. This function is defined with either three or four parameters, depending on whether TICKUNITS is specified.

If TICKUNITS are not specified:

The callback function is called with three parameters: Axis, Index, and Value, where:

Axis is the axis number: 0 for X axis, 1 for Y axis, 2 for Z axis

Index is the tick mark index (indices start at 0)

Value is the data value at the tick mark (a double-precision floating point value)

If TICKUNITS are specified:

The callback function is called with four parameters: Axis, Index, Value, and Level, where:

Axis, Index, and Value are the same as described above.

Level is the index of the axis level for the current tick value to be labeled. (Level indices start at 0.)

Used with the LABEL_DATE function, this property can easily create axes with date/time labels.

[XYZ]TICKINTERVAL

Set this keyword to a floating-point scalar indicating the interval between major tick marks for the first axis level. The default value is computed according to the axis [XYZ]RANGE and the number of major tick marks ([XYZ]MAJOR). The value of this keyword takes precedence over the value set for the [XYZ]MAJOR keyword.

For example, if TICKUNITS = ['S', 'H', 'D'], and TICKINTERVAL = 30, then the interval between major ticks for the first axis level will be 30 seconds.

[XYZ]TICKLAYOUT

Set this keyword to integer scalar that indicates the tick layout style to be used to draw each level of the axis.

0 = The axis line, major tick marks and tick labels are all included. Minor tick marks only appear on the first level of the axis. This is the default tick layout style.

1 = Only the labels for the major tick marks are drawn. The axis line, major tick marks, and minor tick marks are omitted.

2 = Each major tick interval is outlined by a box. The tick labels are positioned within that box (left-aligned). For the first axis level only, the major and minor tick marks will also be drawn.

[XYZ]TICKLEN

Set this keyword to a floating-point value that specifies the length of each major tick mark, measured in data units. The recommended, and default, tick mark length is 0.2. IDL converts, maintains, and returns this data as double-precision floating-point. ZTICKLEN is ignored unless PLANAR is set to 0.

[XYZ]TICKNAME

Set this keyword to a string array of up to 30 elements that controls the annotation of each tick mark. ZTICKNAME is ignored unless PLANAR is set to 0.

[XYZ]TICKUNITS

Set this keyword to a string (or a vector of strings) indicating the units to be used for axis tick labeling. If more than one unit is provided, the axis will be drawn in multiple levels, one level per unit.

The order in which the strings appear in the vector determines the order in which the corresponding unit levels will be drawn. The first string corresponds to the first level (the level nearest to the primary axis line).

"Numeric"

"Years"

"Months"

"Days"

"Hours"

"Minutes"

"Seconds"

"Time" - Use this value to indicate that the tick values are time values; IDL will determine the appropriate time intervals and tick label formats based upon the range of values covered by the axis.

""- Use the empty string to indicate that no tick units are being explicitly set. This implies that a single axis level will be drawn using the "Numeric" unit. This is the default setting.

If any of the time units are utilized, then the tick values are interpreted as Julian date/time values. Note that the singular form of each of the time value strings is also acceptable (e.g, TICKUNITS = 'Day' is equivalent to TICKUNITS = 'Days').

[XYZ]TICKVALUES

Set this keyword to a floating-point vector of data values representing the values at each tick mark. If TICKVALUES is set to 0, the default, IDL computes the tick values based on the axis range and the number of major ticks. IDL converts, maintains, and returns this data as double-precision floating-point. ZTICKVALUES is ignored unless PLANAR is set to 0.

[XYZ]TITLE

Set this keyword to a string representing the title of the specified axis. ZTITLE is ignored unless PLANAR is set to 0.

ZVALUE

For a planar contour plot, the height of the Z plane onto which the contour plot is projected.

Examples

In the IDL Intelligent Tools system, data can be imported from the IDL Command Line (as described in Example 1), or data can be imported via the File menu in the iTool window (as described in Examples 2 and 3). For detailed information on importing data via the iTool file menu, refer to Data Import Methods.

Example 1

This example shows how to use the IDL Command Line to bring contour data into the iContour tool.

file = FILEPATH('convec.dat', SUBDIRECTORY = ['examples', 'data']) 
data = READ_BINARY(file, DATA_DIMS = [248, 248]) 
ICONTOUR, data

Double-click on a contour to display the contour properties. Change the Number of levels setting to 20, change Use palette color to True, and use the Levels Color Table setting to load the EOS B predefined color table through the Load Predefined button in the Palette Editor. Then, change the Fill contours setting to True.

Example 2

This example shows how to use the iTool File ® Open command to load DICOM data into the iContour tool.

Select File ® Open to display the Open dialog, then browse to find mr_brain.dcm in the examples/data directory in the IDL distribution, and click Open.

Double-click on a contour to display the contour properties. Then, change Use palette color to True and the Fill contours setting to True.

Example 3

This example shows how to use the File ® Import command to load binary data into the iContour tool.

At Step 1, select From a File and click Next>>.

At Step 2, under File Name:, browse to find idemosurf.dat in the examples/data directory in the IDL distribution, and click Next>>.

At Step 3, select Contour and click Finish.

The Binary Template wizard is displayed. In the Binary Template, change File's byte ordering to Little Endian. Then, click New Field, and enter the following information in the New Field dialog:

Field Name: data (or a name of your choosing)

Type: Float (32 bit)

Number of Dimensions: 2

1st Dimension Size: 200

2nd Dimension Size: 200

Click OK to close the New Field dialog and the Binary Template dialog, and the contours are displayed.

Double-click on a contour to display the contour properties. Change the Number of levels setting to 10, change Use palette color to True, and use the Levels Color Table setting to load the Rainbow18 predefined color table through the Load Predefined button in the Palette Editor. Then, change the Fill contours setting to True.