how to use <= or >= (greater than or equal to) in 'for statements '?

I want to use these equations in matlab. But it says parse error and might me invalid in matlab.

P = 0.73*x-103.43; for (x>= 141.9)

and

P = 0.06*x-8.04; for (x< 141.9)

Answer 1

[Matt J]

P=nan(size(x));

region=(x>=141.9);

P(region) = 0.73*x( region )-103.43;
P(~region) = 0.06*x( ~region )-8.04;