Matlab accessing global variable from another m file?

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

Answer 1

[Star Strider]

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

[will99]

so I need to declare the variable in both fileB & fileA oh I thought it will be similar to java thank you :)

[Star Strider]

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.