N (Integer, Input) - The number of input data points.
X (Real, Input) - An array containing the X coordinates of the input data points.
Y (Real, Input) - An array containing the Y coordinates of the input data points.
Z (Real, Input) - An array containing the Z coordinates of the input data points.
U (Real, Input) - An array containing the functional values of the input data points. That is,
U(L) is the value of the input function at coordinate (X(L),Y(L),Z(L)), for L=1,N.
M (Integer, Input) - The number of output data points (this may be "1").
XO (Real, Input) - An array of dimension M containing the X coordinates of the output data. The
values in XO may be in any order.
YO (Real, Input) - An array of dimension M containing the Y coordinates of the output data. The
values in YO may be in any order.
ZO (Real, Input) - An array of dimension M containing the Z coordinates of the output data. The
values in ZO may be in any order.
UO (Real, output) - An array of dimension M containing the interpolated values. UO(I) is the
interpolated value at point (XO(I),YO(I),ZO(I)) for I=1,M.
IER (Integer, Output) - An error return value. If IER is returned as 0, then no errors were
detected. If IER is non-zero, then refer to the man page for dsgrid_errors for details.