run multiple linear regression using fitlm without create new table?

I have a large table (500000 rows X 26 columns), there are two category variables, say c1 with value +1, 0 and -1; c2 with value a, b, and c. I need to run 16 regressions using fitlm, which are listed in the table

           ALL a b c
      ALL
      +1
       0
      -1

(ALL, ALL) means using all the data in the table;

(ALL, a) means using data c2 = a, c1 can be any;

(+1, a) means using data c1 = +1 and c2 =a;

so on and so forth.

Right now in my mind, I can pull out the sub-table 16 times from the large tabel, then run the regression.

My question: is there any more efficient way to do this, without creating 16 sub-tables?

Thanks!

Answer 1

[David Barry]

If you need to operate on a subset of the data then ultimately you will need to create that subset of the data. You could try using a categorical array to reduce your memory footprint though.

https://uk.mathworks.com/help/matlab/ref/categorical.html https://uk.mathworks.com/help/matlab/matlab_prog/advantages-of-using-categorical-arrays.html