Sometimes it is necessary to force the programs to have a higher or lower dimension than given in the input file. Forcing a dimension is also important, when the sets or points have different point dimensions.
To force the dimension use the-d option
gr_copy -d 3 -f test.dat
If the point in a set has lower dimension than the current set dimension, the missing coordinate values will be set to zero. Some tools do not allow different dimensions. Those programs will print out a warning.