A signal, by definition, contains information. Any signal obtained from a physical process also contains noise. It is often difficult or impossible to make sense of the information contained in a digital signal by looking at it in its raw form-that is, as a sequence of real values at discrete points in time. Signal analysis transforms offer natural, meaningful, alternate representations of the information contained in a signal.
This section describes IDL's digital signal processing tools. Most of the procedures and functions mentioned here work in two or more dimensions. For simplicity, only one dimensional signals are used in the examples.
The examples in this section are all written to take advantage of IDL Direct Graphics. Examples and techniques using IDL Object Graphics are contained in the later sections of this manual.
The example code used in this section is part of the IDL distribution. All of the files mentioned are located in the examples/doc subdirectory of the IDL distribution. By default, this directory is part of IDL's path; if you have not changed your path, you will be able to run the examples as described here. See !PATH for information on IDL's path.