How do I call a function within another function?

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How do you call a function within a function like
%filename: calculateA.m
function calculateA(arg1, arg2)
%calculations
function calculateB(arg1)
%calculations
end
%calculations
end
where you're trying to call calculateB(arg1) from say, the command window?
  1 Comment
Stephen
Stephen on 22 Jan 2019
@Sterling Baird: your question shows some confusion. You ask "How do I call a function within another function?", but your example shows functions being defined. Calling a function and defining a function are two totally different things:
  • Defining a function:
function y = myfun(x)
y = sin(x);
end
  • Calling a function:
out = myfun(0.1);
Which of these do you actually want to ask about?

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Accepted Answer

David Goodmanson
David Goodmanson on 21 Jan 2019
Edited: David Goodmanson on 22 Jan 2019
[ MODIFIED to use the terminology 'nested functions']
Hi Sterling,
You can define nested functions within other functions as in the following example.
function z = xsixth(x)
z = xsquare(x).^3;
function a = xsquare(b)
a = b.^2
end
end
Here the nested function xsquare is local to the function xsixth, and calling xsquare from the command line results in an error. If for some reason you need the output of (in this example) xsquare, you can either define it as a separate function and no longer a nested function or do something like the following
function [z y] = xsixth(x)
z = xsquare(x).^3;
y = xsquare(x);
function a = xsquare(b)
a = b.^2
end
end
with the extra output y pulling out the result.
  2 Comments
Stephen
Stephen on 22 Jan 2019
Note that David Goodmanson shows a nested function:
The most useful feature of nested functions was not mentioned in this answer: nested functions can access variables in the main function's workspace:
function z = xsixth(x)
a = [];
xsquare(x);
z = a.^3;
function xsquare(b)
a = b.^2
end
end
Local functions are not nested within another function, but are written in the same file:
The different function types are explained in the documentation:
The MATLAB documentation does not use the terminology "subfunction".

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More Answers (1)

Jim Riggs
Jim Riggs on 21 Jan 2019
Your question is asking how to CALL a function from within another function, but your sample code is trying to DEFINE a function within another function. This you can't do. You define the functions in separate files:
%filename calculateA.m
function calculateA(arg1, arg2)
%calculations
..
[] = calculateB(arg) % you may call a function within a function simply by referencing it
% file calculateB.m must be in the Matlab path
end
separate file:
%filename calculateB.m
function calculateB(arg1)
% calculations
...
end
  3 Comments
David Goodmanson
David Goodmanson on 23 Jan 2019
Hi Jim, yes they are limited. The the answer I posted is a means of retrieving the output of the nested function to provide an intermediate result, which seems reasonable. However, I had not quite realized the extent to which the OP wanted to both provide an independent input and retrieve the output of the the nested function. Doing both of those by way of extra input and output arguments of the main function does not seem like good programming practice, and at that point it would make more sense to have an independent function like you were talking about initially.

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