How to use global variables inside a function?

I have declared a global variable outside function. When I wish to use that global variable within a function(without giving it as an input argument), MATLAB is giving an error.

Answer 1

[Basil C.]

First you need to define a variable say x as global

 global x
 x=5

Then in the function definition which is using the global variable x just add the following line and you should be good to go

 function A=hello()
      global x
      A= 5*x;
  end

[Daniela Ardila Ospina]

Thank you so much!

[tuan nguyen minh]

oh thanks so much, your answer helps me

Answer 2

[Image Analyst]

It works for me. Did you declare the variable as global inside the function? You have to. If you did, then you must have a "clear all" or "clear global" in your function. Get rid of the clear statement and it will work.

See informative comments below in the code:

% Main.m
global y;
y = 10;
out1 = func1(7)
out2 = func2(9)

%==================================================================================
% func1.m -- can see y.  Declared y global so this function can see it.
function out = func1(z)
global y; % Declare y as global at beginning so the rest of the function can see it.
z = y; % Will NOT throw an error because y is declared global inside func1().

%==================================================================================
% func2.m -- can NOT see y.  NOT declared y global so this function can NOT see it.
function out = func2(z)
z = y; % Will throw an error because y is not declared global inside func2().

%==================================================================================
% func3.m -- can NOT see y.  NOT declared y global so this function can NOT see it.
function out = func3(z)
global y; % Declare y as global at beginning so the rest of the function can see it.
clear global % DO NOT do this.  Doing this will remove the ability of func3() to be able to see y!!!
z = y; % Will throw an error because y is not longer seen inside func3().