In array mode (SINGLE=FALSE), statistics are calculated for each pixel in one of the array components (DATA, VARIANCE or QUALITY) accumulated over all the input NDFs and written to an output NDF; each pixel of the output NDF is a result of combination of pixels with the same Pixel co-ordinates in all the input NDFs. There is a selection of statistics available to form the output values.
The input NDFs must all have the same number of dimensions, but need not all be the same shape. The shape of the output NDF can be set to either the intersection or the union of the shapes of the input NDFs using the TRIM parameter.
In single pixel mode (SINGLE=TRUE) a position in the current co-ordinate Frame of all the NDFs is given, and the value at the pixel covering this point in each of the input NDFs is accumulated to form the results that comprise the mean, variance, and median. These statistics, and if environment variable MSG_FILTER is set to VERBOSE, the value of each contributing pixel, is reported directly to you.
The value must be positive. [3.0]
Where needed, the co-ordinates are the indices of the input NDFs in the supplied order. Thus the calculations behave like the NDFs were stacked one upon another to form an extra axis, and that axis had GRID co-ordinates. Care using wildcards is necessary, to achieve a specific order, say for a time series, and hence assign the desired co-ordinate for a each NDF. Indirection through a text file is recommended.
The selection is restricted if there are only a few input NDFs. For instance, measures of dispersion like "Sigma" and "Iwd" are meaningless for combining only two NDFs. The minimum number of input NDFs for each estimator is given in parentheses in the list above. Where there is no number, there is no restriction. If you supply an unavailable option, you will be informed, and presented with the available options. ["Mean"]
No warning is given when Parameter WLIM=0. Input data containing only bad values are not counted in the flagged fraction, since no potential good output value has been lost.
KAPPA --- Kernel Application Package