function where input is also output

Is it possible to have a function where the argument is also calculated in the same function?

[Mathieu NOE]

I don't think so

for me a function has always distinct input and output arguments - what are you trying to achieve ?

[Marina]

I'm trying to calculate a temperature using a flow. Once the temperature is found, I'd like to recalculate this flow to use it for the next calculation... and so on.

[Mathieu NOE]

ok then you can do it by iterations and hopefully it should converge , like

% start with initial values of flow and temperature
temp = ...
flow = ...

tol = 1e-3; % tolerance on result - whatever you want 

while error > tol  % repeat the loop until results have converged
    temp_new = function1(flow); % update temperature (with function1)
    flow_new = function2(temp_new); % update flow     (with function2)
    % compute error 
    error = abs(flow_new - flow) + abs(temp_new - temp); % other error metrics are possible, this is just one example
    % update flow / temp 
    flow = flow_new;
    temp = temp_new;
    
end

[Marina]

I will try . Thanks

Answer 1

[Star Strider]

You can certainly return the input as an output if you want to.

A simple example —

x = 42;
[result_val, arg_val] = square_arg(x)

result_val = 1764

arg_val = 42

function [result_val, arg_val] = square_arg(x)
arg_val = x;
result_val = x.^2;
end

.

[Marina]

Thanks . I will try something like that

[Star Strider]

My pleasure!

Answer 2

[Kunal Kandhari]

Hi Marina,

I understand that you are seeking to utilize pass-by-reference to modify the input argument passed into a function. The answer to the question depends on whether the input is a handle object or a value object.

The following MATLAB Answers post will explain how to achieve that:

https://in.mathworks.com/matlabcentral/answers/152-can-matlab-pass-by-reference

[Marina]

Thanks you. I'll watch it right now