Please answer! How to use an if function effectively?

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Et.B200 le 9 Nov 2020
Commenté : Stephen23 le 10 Nov 2020
Hi everyone,
I have a set data loaded into the workspace at 4x100, using the if function to analyse a certain colomn within that data to see say if any value is say greater than 2, and then say if a number within that coloum is greater than 2 then set a number on that same line from a different colomn say in the second coloum to a variable.
Eg, say coloum 4 is the colum i want to analyse, to see if any number in that colum is greater than 2, say lines 30, 67 and 80 are greater than 2, i want the function to then set column 2 values from lines 30, 67 and 80 to a variable lets say x. If that makes more sense
Thank you!

Réponse acceptée

dpb le 9 Nov 2020
Modifié(e) : James Tursa le 9 Nov 2020
colmn_analyze=4; % desired column to compare
colmn_target=2; % desired column to set
valLimit=2; % limiting value
% engine
ix=(A(:,colmn_analyze)>valLimit); % logical vector of locations match condition
A(ix,colmn_target)=x; % set the target column locations to value of x
NB: x must either be a scalar or a vector of length of TRUE elements in ix in the order to match or will have a number elements mismatch on the assignment.
Read up on logical indexing in the Getting Started doc for a most useful feature in MATLAB.
  7 commentaires
Et.B200 le 9 Nov 2020
Ohh sorry, i've just worded my question wrong!! Sorry guys! So I want the output, using your example, to be the numbers 1.2684, 3.8009, and 0.1378, not to change the data set as such, but to output the numbers on the same line as those in another column which suit the value limit.
Many thanks, Ethan
James Tursa
James Tursa le 9 Nov 2020
Do you mean like this?
colmn_other = 6;
A(ix,colmn_other) = A(ix,colmn_target)

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