Why do global variables not update in the Workspace Browser or the Array Editor when I modify them from within a function?

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MathWorks Support Team 2009-6-27

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评论： Nalini Vishnoi 2015-7-13

I declare a global variable "A" in the base MATLAB workspace and assign it a value as follows:

global A
A=1;

The workspace browser shows "A" is equal to 1. I open the variable "A" in the array editor and see that the correct value is displayed here as well. I assign a new value to "A" from the command line as follows:

A=2;

I see that both the workspace browser and the array editor show the correct value for "A". Now I modify "A" using an M -file function as follows:

function seta(x)
       global A
       A=x;

When I modify "A" using the function "seta", the Workspace Browser and Array Editor do not get updated with the correct value of "A". When I just type "A" at the Command Line the Array Editor updates, but the Workspace Browser does not. I need to right click in the Workspace Browser and select Refresh from the Context Menu to update the value of "A". If I assign a new value to "A" from the Command line as follows:

A=5;

both the workspace browser and the array editor will update correctly regardless of any updates I have made using "seta".

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Answer 1

MathWorks Support Team 2009-6-27

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This bug has been fixed in Release 14 Service Pack 2 (R14SP2). For previous releases, please read below for any possible workarounds:

We have verified that there is a bug in MATLAB 7.0.1 (R14SP1) that affects the way the values of global variables are updated in the Workspace Browser and the Array Editor when they are modified from within a function. The values of global variables update correctly when the variables are modified in the base MATLAB workspace, i.e., from the command line. This issue has been forwarded to our development team for consideration for a future release of MATLAB.

To work around this problem, use EVALIN as follows:

function seta(x)
       global A
       A=x;
       evalin('base','A=A;');

This forces the update by executing the assignment statement, "A=A;", in the base MATLAB workspace.

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Answer 2

timo 2015-4-25

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I think I am getting this bug in 2015a again lol :(

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Nalini Vishnoi 2015-7-13

Hi Timo,

I was not able to reproduce the same behavior in MATLAB R2015a. I would recommend to contact MathWorks Technical Support if you continue to see this issue. I hope this helps.

Nalini

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