make matlab variable in workspace as global

Question

In the workspace I make a matrix .

Now I can access the variable in script. Like doing Variable(2) will return 4.

But inside a function like

function y= getvariable(x)

y=Variable(x)
end

I get error

   y=getvariable(2)
    ??? Undefined function or method 'Variable' for input
    arguments of type 'double'.

    Error in ==> getvariable at 3
    y=Variable(x)

So how to make the Variable matrix global so that I can access it through any function?

Answer 1

Although you could use globals

>> global Variable = rand(50,12);

...

function y = getvariable(x)

     % Always needed
     global Variable;

     % Here ya go
     y = Variable;

end

the MUCH better alternative is to use

function x = getvariable(x)
     % no body needed    
end

which you call as

>> y = getvariable(Variable);

(Of course, for this contrived example, this would just be equal to

>> y = Variable;

)

Although there are some legitimate use cases for global variables, in general they tend to spaghettify your code and make it far more bug-prone and much harder to debug. Have a read on the subject.

Answer 2

As @rody suggested, pass the matrix and the x inside the function

I am just giving an example to make things clear.

Like you want to access the 10th element of Variable matrix, so make the function as

function y= getvariable(matrixname,no)
y=matrixname(no)
end

If you want to access 3rd element of Variable, so you type

y=getvariable(Variable,3)

you will get 3rd element

Answer 3

1. call global Variable before you define it in your workspace
2. call global Variable before you use it in your function

However I suggest you think of other ways to pass variables to your function, as globals might cause difficulties during debugging.