The following enhancements have been made to IDL's data analysis functionality for the 6.1 release:
In addition to the previous additions, in IDL 6.1 several wavelet routines that were part of the Wavelet Toolkit have been integrated into the core IDL product. The Wavelet Toolkit is still available, but now provides only a GUI for wavelet analysis. The wavelet functions that are now part of the IDL library are:
The new UNSHARP_MASK function lets you apply unsharp-mask sharpening filters to two-dimensional arrays or TrueColor images. Digital Unsharp Masking is a digital image processing technique that increases the contrast where subtle, fine details are set against a bright, diffuse background. The digital process works by subtracting from the original image an "unsharp mask" created by digitally blurring or smoothing a copy of the original image. This operation suppresses features which are smooth (those with structures on large scales) in favor of sharp features (those with structure on small scale), resulting in a net enhancement of the contrast of fine structure in the image. The following figure shows the original image (left) and filtered image (right).
See UNSHARP_MASK for more information.
New functionality has been added to IDL 6.1 to support hierarchical cluster analysis and dendrite plotting (dendrograms). Hierarchical clustering joins together data points into successively larger clusters, using a distance (similarity) measure and linkage rules. This technique is of great importance in data exploration, as it allows researchers in a wide variety of fields to distill large amounts of multi-dimensional data down into more manageable and meaningful segments.
The following figure shows a sample dendrogram created using the new cluster analysis functionality.
The new CLUSTER_TREE, DENDRO_PLOT, DENDROGRAM, and DISTANCE_MEASURE routines all support this new functionality. For more information, see CLUSTER_TREE, DENDRO_PLOT, DENDROGRAM, and DISTANCE_MEASURE.
The new INTEGER and PRESERVE_TYPE keywords to the PRODUCT and TOTAL routines allow you to use integer arithmetic and generate an integer result. See PRODUCT and TOTAL for more information.
In very "noisy" images (images with a very high number of watersheds), the number of regions may exceed the default short integer maximum return value of 32766 regions. Two new keywords have been added to gracefully deal with such cases:
See WATERSHEDfor more information.
A new DOUBLE keyword adds double-precision support to the SPLINE and SPLINE_P routines, allowing you to carry additional significant digits when needed. Additionally, enhancements have been made to the Xr and Yr arguments for SPLINE_P. For more information on this new support, see SPLINE and SPLINE_P.
A new DOUBLE keyword adds double-precision support to the MEDIAN function. This provides support when passing very large integer inputs. Additionally, enhancements have been made to the Array argument. For more information, see MEDIAN.
A new ABSOLUTE keyword to the MIN and MAX functions allows you to use absolute values when comparing data elements for both real and complex inputs. For more information, see MAX and MIN.
A new MISSING keyword to the BILINEAR function lets you specify what value to return for data elements which are outside the bounds of an input array. For more information, see BILINEAR.
The NORM and COND functions now support complex data input. For more information on this functionality, see the entries for COND and NORM.
The Besel functions can now handle negative inputs. The existing documentation has been updated in the IDL Reference Guide under the individual BESEL functions.