Percentage difference in matlab

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.

Answer 1

[Nicolas B.]

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