Jinsong,
For positive correlation, try
3dTcorrMap -input input_data -mask mask_data -Cexpr 'step(r)*r' output_data
Similarly for negative correlatoin:
3dTcorrMap -input input_data -mask mask_data -Cexpr 'step(-r)*r' output_data
Gang
Edited 1 time(s). Last edit at 03/03/2017 09:23AM by Gang.