Keep a variable in workspace when calling a function

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Dingguo Lu
Dingguo Lu 2011-11-12
回答： Andrej Sternin 2020-4-11
My question is how to keep a variable in a called function into the workspace.
I was told the code can be written using persistent memory inside the function.
As known, when calling a function, all the variables will be cleared after the function is called, i.e., no variables will appear in workspace.
Can anybody tell me how to work on it.
Thanks in advance.
  1 个评论
Sven
Sven 2011-11-12
Yes, there is a thing called a "persistent variable".
Is this what you would like to use?

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回答（3 个）

Andrej Sternin
Andrej Sternin 2020-4-11
https://de.mathworks.com/help/matlab/matlab_prog/base-and-function-workspaces.html
the cyclist
the cyclist 2011-11-12
I don't perfectly understand what you mean, but I can think of three possibilities that might help you:
  • Send the variable as output
  • Use a global variable
  • Use the assignin() function
You should easily be able to find information about all of these in the documentation.
Jonathan
Jonathan 2011-11-12
The code below uses a persistent variable. The first time the function is run, the variable is given the value [] (the empty matrix).
function out = testPersistent()
persistent x
if isempty(x)
x = 1;
else
x = x + 1;
end
out = x;
end
When I run the function several times, this is what the output looks like.
>> testPersistent()
ans = 1
>> testPersistent()
ans = 2
>> testPersistent()
ans = 3
I hope this helps.

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