
To extract a subarray from a matrix apply extractitem to the array of real of the matrix.
For instance to extract a rectangular subarray you would specify a step parameter equal to the matrix' ncols.

To extract rows from a matrix apply extractitem to the matrix itself.

To extract columns from a matrix apply extractcolumn to the matrix.
By default, when applied to a matrix, extractcolumn will return one array of real if you extract one column, or one list of arrays of real if you extract more than one column.

To extract columns from a matrix and get the subarray as a matrix, specify extractcolumn [...] as matrix.

To extract columns from a matrix and get the subarray as a tabulated (tab and returndelimited) string, specify extractcolumn [...] as string.

Use the skipping parameter (for instance: skipping 1) to skip the header row(s).
