Checking parameter value in a function

Question

Clement Koh 2020-11-8

0
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https://ww2.mathworks.cn/matlabcentral/answers/640895-checking-parameter-value-in-a-function

编辑： Sreeranj Jayadevan 2020-11-11

Hi all!

Suppose I have a few parameters in a function file of ODEs. And given that I have set a parameter (for e.g 'Var_A') to change according to time. Are there any ways that I can retrieve the value of the parameter over a period of time and plot them? I just want to show that the parameter change over a period of time.

Pls advise whoever knows this. Thank you :)

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Answer 1

Sreeranj Jayadevan 2020-11-11

1
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https://ww2.mathworks.cn/matlabcentral/answers/640895-checking-parameter-value-in-a-function#answer_541195

编辑：Sreeranj Jayadevan 2020-11-11

在 MATLAB Online 中打开

An easy way to achieve this is to create a scalar variable and then to gradually increase the size over time while you execute the code. For example, if you wish to store the value of 'Var_A' after each iteration (with respect to time in this case) you can concatenate the new values over time and create a 1-D array. i,e

Arr=0;
for i=1:n
    % Various operations your function performs. Var_A gets updated here 
    Arr(i)=Var_A;
end

'Arr' will contain the required values which you can plot with respect to time.

Note: This approach is however not recommended if 'n' is a large value as this leads to repeated reallocation of memory by MATLAB. You can go through the following link for more information: https://in.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html

A alternative method which is more efficient would be to initialize the array/vector beforehand and populating the initialized array during execution. If you know how many elements the vector will contain after execution, you can initialize the vector.