How to define a variable that store its value after closing MATLAB file?
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Hi,
I just want to declare a variable that holds its value through the whole file and even after closing it , also to initialize it externally . I tried to use 'persistent' variables but they're locally defined and so I have to initialize it locally , that makes its value initialized each time the function is called. When I define it global to avoid the repeated initialization through the same file , a warning appears 'the variable can apparently be used before it's defined' and an error 'undefined variable'. I need this variable to save txt files that contains the incremented variable value in its name.
Thanks in advance
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Nathaniel
2012-9-17
If you're getting undefined variable errors for something you thought was supposed to be a global, then you haven't defined it to be global in the current context/scope.
function myfun
global param
if isempty(param) % hasn't been initialized
param = 1;
else % already initialized
param = param + 1;
end
% do something useful
So with that explained, why don't you simply pass in the value as an argument to the function? Using globals is generally frowned upon, since it can become difficult to keep track of which functions are using which globals and then when you start getting incorrect answers, it can take a lot of time to figure out why (if you're lucky enough to even notice that they're incorrect).
Jan
2012-9-18
编辑:Jan
2012-9-18
function out = myFunc(in)
persistent Data
if nargin == 0
Data = rand(10);
if nargout > 0
out = Data;
end
return;
end
... Your calculations come here
Now the persistent variable is initialized by:
myFunc;
And exported by:
data = myFunc;
And a standard call of the function is:
theOutput = myFunc(theInput);
I avoid working with GLOBALs strictly. They cause too much interferences and in larger programs it is the hell to find out, which subfunction had written the last changes.
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