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Diffstat (limited to 'math/interp/overview')
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diff --git a/math/interp/overview b/math/interp/overview new file mode 100644 index 00000000..4ad813ca --- /dev/null +++ b/math/interp/overview @@ -0,0 +1,43 @@ +Interpolation Package + + The routines here are intended to allow programmers to interpolate +one dimensional arrays and two dimensional +images in the IRAF system. The routines are +mathematical in nature and are not heavily tied into the IRAF package. +The advantages of having locally written interpolators include the +ability to optimize for uniformly spaced data and the possibility of +adding features that are useful for the final application. The +one major feature that has been implemented is the ability to change +the kind of interpolator used at run time by carrying along a variable +that gives the interpolator type in the higher level code. + + The kinds of interpolators include: + 1. Nearest neighbor + 2. Linear + 3. Interior polynomial order = 3 + 4 Interior polynomial order = 5 + 5 Spline order = 3 + + The package is divided into array interpolators and image +interpolators. Within the array interpolators, there is further +division into sequential and random interpolators. The sequential +interpolators are optimized for returning many values as is the +case when an array is shifted or when an array is oversampled +at many points in order to produce a smooth plot. The random interpolators +allow the evaluation of a few interpolated points without the computing +time and storage overhead required for setting up the sequential version. + + The original specification called for the interpolator package +to deal with indefinite valued pixels and references out of bounds. +A version of the array sequential interpolators was written that handled +both situations allowing some options to the user. The extension of +these features to the two dimensional case becomes more dependent on +details within IRAF and less mathematical in nature. It would also +duplicate other code within IRAF that deals with out of bound references. +Finally the need to test for the various situations slows down the operation. +So all features referring to indefinite valued pixels and out of bound +references have been removed. The user is responsible for ensuring that +"x" values land within the array. The code does not test to see if x +is in bounds. A routine has been added that interpolates +an array with indefinites and returns an array with all legitimate +real numbers. |