Hi Daniel,

Thank you very much for answering this! I have a question about the 3dcalc operation:

I don't to repeat indices if they've already been summed. e.g. I want to only sum points 1 & 2, then 3 &4, 5& 6, and so on. Not 1 & 2, then 2&3, then 3&4, etc. as is done in the above setting. Thus my new data set would have a reduced time length of n_t/2 where n_t is the number of time points in the original data set. In the 3dcalc, is it possible to make the 'b' data set to be '2*a-l'. That is an invalid operation, I've come to find, but something like that would be great.

I suppose I could try to collect every 2nd point of the output data set from the above command you listed with 3dcalc, but I'm not sure how to do that either.

Thank you for your help!

Cheers,
Edwin