Reduce Matrix by Adding Every Nth Rows and Nth Columns

Good morning everyone!

I was hoping for suggestions regarding a matrix reduction problem. I have a matrix that is 8000 x 4000. I would like to produce a new matrix that is 400 x 100 by adding every nth rows and nth columns. That is, I would like to reduce the number of rows from 8000 to 400 by adding every twenty rows, and I would also like to reduce the number of columns from 4000 to 100 by adding every 40 columns. Is there a direct way of doing this? I've tried to reshape the matrix, but the new matrix produced would have the same size as the original. (I'm pretty sure it's rather easy, but I can't seem to function too well at this moment...)

Any help would be greatly appreciated! Thanks for everything!

[madhan ravi]

how many submatrices do you want to create from 8e3 X 4e3?

[Michelle De Luna]

Madhan Ravi, thank you for the follow-up question. David pointed out a rather simple solution. Again, thank you for your help!

Answer 1

[David Hill]

m=m(1:20:8000,1:40,4000);

[Michelle De Luna]

David, thank you for your quick response! I appreciate your help! As always, thank you!