Spatial average over X and/or Y of a vector/scalar field
FF = spaverf(F) computes the spatial average of the vector/scalar
field F. FF is a uniform vector/scalar field. If F is an array of
fields, spaverf(F) computes the individual spatial average of each
FF = spaverf(F,AXIS) averages over the AXIS direction, where AXIS is
'X', 'Y' or 'XY'. Default is 'XY'. FF is a vector/scalar field uniform
in the AXIS direction.
By default, spaverf considers that the zero elements of F are erroneous,
and does not include them in the computations. If however you want to
force the zero elements to be included in the computations, specify
If no output argument, the result is displayed by showf.