How to use global variables inside a function?

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Saraswatula Sai Pavan Sastry Sastry SOME
编辑： Image Analyst 2021-10-26
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.

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回答（2 个）

Basil C.
Basil C. 2018-9-27
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
Image Analyst
Image Analyst 2018-9-27
编辑：Image Analyst 2021-10-26
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().

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