Loading data in a function and passing it

Question

Richard Prince 2017-2-24

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评论： Richard Prince 2017-2-24

Hello all. I'm trying to write a function that checks for the existence of a series of variables. If they exist, I want the function to do nothing. If they don't exist, I want the function to load them into the workspace and pass them to the main workspace. When I run my code however, it loads the first file and assigns it to variable ans. Any help is appreciated.

function [cntREF, sREFn, w] = LoadClassData
%%%%Loads the preset data created by the training algorithm
   if exist('B', 'var') == 1
       return;
   else
      load('B.mat');
   end
if exist('cntREF', 'var') == 1
    return;
else
     load('cntREF.mat');
end
if exist('sREFn', 'var') == 1
    return;
else
    load('sREFn.mat');
end
if exist('w', 'var') == 1
    return;
else
    load('w.mat');
end
end

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Richard Prince 2017-2-24

Also I should mention above that when I run the function with the variables already in place it is executing the else statements anyway. Is this some kind of local workspace problem?

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Answer 1

Jan 2017-2-24

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https://ww2.mathworks.cn/matlabcentral/answers/326701-loading-data-in-a-function-and-passing-it#answer_256158

在 MATLAB Online 中打开

Each function has its own WorkSpace. Because your function does not have any input, there are no variables defined at the beginning:

function [cntREF, sREFn, w] = LoadClassData
if exist('B', 'var') == 1
   % Cannot happen under any circumstances
end

Now you can load the MAT file to the variable B, but it is not provided as output and therefore it does not appear in the caller. The is the meaning of functions: hide everything, what happens internally except for inputs and outputs.

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Richard Prince 2017-2-24

Thanks that clears it up quite a bit. Is there a way to effectively implement what I want in a function, or should I just move all the if-statements into the body of the main code?

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Answer 2

kowshik Thopalli 2017-2-24

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In the else condition- write b=load('b.mat'), w=load('w.mat') etc. Does this solve your problem?

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Richard Prince 2017-2-24

No this changes the datatype of the variable being loaded. Also I should mention above that when I run the function with the variables already in place it is executing the else statements anyway. Is this some kind of local workspace problem?

kowshik Thopalli 2017-2-24

Yes You are right. It becomes a structure.You have to then access using b.b; Yes. Functions have their own work space which is different from base workspace . Return the loaded matfiles to the script that calls this function.

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