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Percentage difference in matlab

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Sarah K
Sarah K on 23 Oct 2019
Edited: Nicolas B. on 23 Oct 2019
Hi,
I have two variables (both scaler input) to use in a formula. How can I calculate the percentage difference between and make a 'if percentage difference is higher than x%, display 'good' etc. Maybe I must use a loop? Thank you.

Answers (1)

Nicolas B.
Nicolas B. on 23 Oct 2019
Edited: Nicolas B. on 23 Oct 2019
Hey Sarah,
The following code could help you:
diff = x2 - x1; % x2 and x1 are your input variables. x1 is reference and x2 the value to compare
relDiff = diff / x1;
if abs(relDiff) > tolerance % e.g. 0.01 for 1%
disp('good');
else
disp('bad');
end
This code is based on the assumption that x1 and x2 are scalar. If x2 is not scalar (x1 can be scalar or same size as x2):
relDiff = (x2 - x1) ./ x1; % it is not a matrix division but an element-wise division
[I, J] = find(abs(relDiff) > tolerance); % return all indexes of elements that are out of range
% check if any value is out of range
if ~isempty(I)
% display the list of values out of range
for n = 1:numel(I)
fprintf('Index [%d,%d] is out of tolerance'. I(n), J(n));
end
else
% display good because all values are in the range
disp('good, here have a biscuit :)');
end
Hope it helps
Regards

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