Program: DECIM Purpose: Decrease size of a set in any direction with an integer factor Category: MANIPULATION, CALCULATION File: decim.c Author: M. Vogelaar Keywords: INSET= Give set (, subsets) to decimate: Maximum number of subsets is 2048. BOX= Frame for input subsets. [entire subset] DECIM= Give decimation: [1,...] The user can specify a decimation factor for each axis in a subset. The default value for each axis is 1. Negative values are not allowed. ** SHIFT= Shift in start of decimation: [0] Specify which of the 'decim' number of pixels will be transferred to the new created output pixel. If for example a decimation factor 3 is specified, the pixels 0, 1, 2 create a new output pixel containing the value of the original pixel 0 by default. However, if the user wants to transfer one of the other pixels, he has to specify a shift. For the decimation factor 3 the shifts 1 and 2 are allowed. Of negative shifts, the absolute values are taken and of shift values greater than (decimation - 1) the modulus is calculated. OUTSET= Give output set (, subsets): Output set and subset(s) for the result. The number of output subsets is the same as the number of input sub- sets. Description: Decimate data in each specified direction of a subset. The decimation factor must be an integer number. In the output, pixel 0 will always be retained. If for example the user specified the decimation factor 3, then the pixels -9, -6, -3, 0, 3, 6, 9 etc. will be in the output. If he also specified for this axis a shift of 1, the pixels -5, -2, 1, 4, 7 etc. will be transferred. A possible use of the shift could be the creation of sets made with different shifts to combine them to a new set with flux that can be compared to the flux of the original (not decimated) set. Example: Updates: ... .., 1990: VOG, Document created. jun 11, 1996: VOG, Bug in output size removed. Oct 1, 1996: VOG, DECIM could not handle subsets: out=0 initialisation was move from outside to inside subset loop.