IDL includes a number of routines based on algorithms published in Numerical Recipes in C: The Art of Scientific Computing (Second Edition). Routines derived from Numerical Recipes are noted as such in the IDL Reference Guide and in the IDL Online Help.
In IDL versions up to and including IDL version 3.6, mathematics functions based on Numerical Recipes algorithms required that input be in column-major format. This is no longer the case. Routines based on Numerical Recipes algorithms have been reworked and renamed, so that all IDL functions now expect input arrays to be in row-major format (composed of row vectors).