15.5.104 compress

compress(data [, dimensions], factors)

Returns a compressed copy of array data, which may have an arbitrary number of dimensions. The positive integer compression factors are taken from factors and the dimensions that these factors are applied to are taken from dimensions, which defaults to indgen(factors). If factors contains a single number and dimensions is not specified, then the compression factor is applied to all dimensions.

The result is of the same data type as data. Each element of the result contains the average of a fixed number of neighboring elements of data indicated by fctors and dimensions. Of each dimension of data, the first part is treated that has a size equal to the greatest multiple of the compression factor for that dimension that fits the dimension of data. For example, if data is an array of 11 by 7 elements and factors contains the numbers 4 and 2, then the result will have dimensions 2 (= fix(11/4)) by 3 (= fix(7/2)), and the part of data that is treated is indicated by the range (0:7,0:5). The first element of the result will be equal to the average of data(0:3,0:1).

See also: expand, regrid, regrid3, Interpolation, Array Manipulation

Note: The invocation of this version of compress is not backwardly compatible with the old one, which treated two-dimensional data only. The old version was called like this: compress ( data, xfac [, yfac]) where xfac and yfac were the compression factors for the first and second dimensions, respectively, and yfac defaulted to xfac.