Dear Sagi,

Thanks for your kind help.
Yes. It perfectly worked for me. However, I had to change two lines of your code in order to save my data.
I changed these two lines:
P.fname.nirs = [pathName,'/NIRS_',prevName,'.mat'];
P.fname.pos = [pathName,'/POS_',prevName,'.mat'];

to:
P.fname.nirs = [pathName,'NIRS_',prevName,'.mat'];
P.fname.pos = [pathName,'POS_',prevName,'.mat'];

Thank you.

Bests,
Bahareh