# Length/Index based if else statements

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Fawad Farooq Ashraf on 1 May 2022
I have a vector of variable length, for example
b = [0.25;0.5;0.75;1;1.5;1.75;2.0];
and based on the length of this vector, I have some specific parameter K against each element of b, x is the input and my final output is m
if x < b(1)
m = K(1);
elseif x < b(2)
m = K(2);
elseif x < b(3)
m = K(3);
elseif x < b(4)
m = K(4);
elseif x < b(5)
m = K(5);
elseif x < b(6)
m = K(6);
else
m = K(7);
end
I want to generalize my code based on the length of b. Here, the length was 7 so I had to run it manually like this for 7 elements. How can I generalize this for any length of b?

Voss on 1 May 2022
Edited: Voss on 1 May 2022
idx = find(x < b,1);
if isempty(idx)
idx = numel(b);
end
m = K(idx);
The above assumes b is sorted in ascending order, as in the example. If b is not necessarily sorted, you'd have to sort it first.
##### 3 CommentsShow 1 older commentHide 1 older comment
Joe Jones on 27 Jul 2022
Dear
Have you solved this problem? I met the error recently.
compilation of model failed while trying to resolve underspecified signal dimensions
Fawad Farooq Ashraf on 30 Jul 2022
@Joe Jones I guess you have to use the "Ports and Data Manager" for that. In the editor window for MATLAB Function, click on "Edit Data" and then try to specify the type and size. That should work for you.

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