Selecting from a range of values from a column matrix

I have a column matrix (398404 x1). I want any values less than 42 between rows 290360 and 380876 to be 5 while values outside those rows remain the same. Please I need help. Thank you.

Answer 1

[Walter Roberson]

r1 = 290360; r2 = 380876;
extract = YourMatrix(r1:r2);
extract(extract < 42) = 5;
YourMatrix(r1:r2) = extract;

or...

r1 = 290360; r2 = 380876;
rowidx = (1:numel(YourMatrix)).';
mask = rowidx >= r1 & rowidx <= r2 & YourMatrix < 42;
YourMatrix(mask) = 5;

[Austin Ukpebor]

It works! Apart from array indexing, what other areas would you recommend I read up?

Thank you.