Proportional change of values with a fixed sum

Hi!

I´m new using Matlab want to know how to express in the software the change of percentages when I modify one of the values and I have a fixed sum (100%).

Say for example that I have: a= 50%, b=25%, c=25% and the sum is 100%. If I remove a, then values b and c will change into 50% to get the sum of 100%.

Answer 1

[Roger Stafford]

To put your problem in general terms, suppose you have a row vector of values, v, with some given sum. For the i-th element you wish to change from v(i) = vi1 to v(i) = vi2 and adjust the remaining elements proportionally so as to retain the same overall sum. Then do this:

s = sum(v);
f = (s-vi2)/(s-vi1);
v = [f*v(1:i-1),vi2,f*v(i+1:end)];

Then v should have the same sum as before (except for possible tiny rounding error differences.) (We assume that the sum is different from vi1.)

[Sandra Cortes]

Oh I see. Thank you so much for your help!! I applied it by changing several values at the same time and works perfectly!