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will99
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Matlab accessing global variable from another m file?

Asked by will99
on 7 Oct 2015
Latest activity Commented on by Star Strider
on 7 Oct 2015
so let say I have two files fileA.m & fileB.m in fileA.m I have this code
function fileA()
global dataX;
dataX = 100;
end
in fileB.m I want to use if to check the value this is what I have in fileB.m
function fileB()
if dataX == 100
fprintf('Value is %f \n' , dataX);
else
fprintf('Value is NOT %f \n' , dataX);
end
end
however I'm having problem every time I run fileB.m I get this error Undefined function or variable 'dataX'.
so how can I access global variable from another .m file .. I'm new to Matlab

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1 Answer

Answer by Star Strider
on 7 Oct 2015
 Accepted Answer

Please do not use global variables!
However if you must, you have to declare them as globals in every workspace that uses them. They don’t just magickally appear!
function fileB()
global dataX
if dataX == 100
fprintf('Value is %f \n' , dataX);
else
fprintf('Value is NOT %f \n' , dataX);
end
end

  2 Comments

so I need to declare the variable in both fileB & fileA oh I thought it will be similar to java thank you :)
My pleasure.
MATLAB has its own rules about such things as globals. It is still best to pass ‘dataX’ and anything else your function needs as an argument rather than a global.

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