HOW to Overwrite Matrix Values in a loop, not Append!! ??

Hi guys! Hope you are doing great!

Well I run this particular code with the 4 matrices out_M, out_M_corr, out_R and out_R_corr.

(I have attached an EXCEL file - 'sample.xlsx' to show these matrices).

out_M_corr = out_M;
out_R_corr = out_R;
out_M_corr(:,3) = out_M_corr(:,3)*2;          %these are the correction factors.....
out_M_corr(:,5) = out_M_corr(:,5)*5.3346;

for nR=1:size(out_R,1) 
    test = (out_M_corr(:,1) == out_R_corr(nR)); 
    val = find(test,1,'first'); 
    out_M_corr(test, 2) = out_M_corr(test, 2) - out_M_corr(val,2); 
    X(test,1) = out_M_corr(test,2); 
    Y(test,1) = out_M_corr(test,3); 
    poly = polyfit(X,Y,1); 
    out_R_corr(nR,4) = poly(1,1); 
    out_R_corr(nR,3) = poly(1,2); 
end

The problem I am facing is in the loop. I want the matrices X & Y to always store new values and overwrite the values from previous iteration of the 'for' loop.

But to my surprise it is APPENDING, not OVERWRITING.. :( What can be the problem?

I would really appreciate your inputs!! PLEASE help!

Regards

Pramit

Answer 1

[Jan]

What about this:

X = out_M_corr(test,2); 
Y = out_M_corr(test,3);

[pramit Sood]

Hey Jan!!

Well I can't help but give thumbs up to you to teach me that thinking simple is the best idea!! It works! :D

Thank you so much!! N Happy Easter!!! Can I send you some chochlates?? :)

Regards

Pramit

Answer 2

[Roger Stafford]

If you want X and Y to be completely overwritten on each trip through the for-loop, you will have to make some provision for their values for the elements for which 'test' is false. Otherwise these "false test" elements, though initially zero, will thereafter be what they were on the previous pass. Probably you should do something like this:

   X = zeros(size(out_M_corr,1));
   X(test,1) = out_M_corr(test,2);

and similarly for Y.

[pramit Sood]

Hi! thank you for your reply.. :) Unfortunately that does not help.. as I had tried doing it earlier.. It gives '0's for the old values.. what I want is the old values to be completely deleted and only new values from the current iteration to remain.. :)

Regards

Pramit

[pramit Sood]

Hi Roger!

Thank you for the initiative to help me!!

Joyful easter holidays to you!!

Regards

Pramit