Clear function works in command window but not in script file

Hello everyone,

I am facing a weird problem here with the CLEAR function. I am generating a string using the following function:

varname=strcat('time',num2str(get(popupmenu1, 'Value')))

I am then using the following function:

clear (varname)

However, I do not get any error, but the variable is not deleted. On the other hand, when I just type the above command directly in the command window, the variable is deleted!

How comes?

Answer 1

[Walter Roberson]

Leave out the (), just

clear varname

[Matt]

Thank you for your quick answer. I've tried and it doesn't work. I do not get any error message, but the variable is not deleted from the workspace.

And if I enter this command in the command window, the variable "varname" is deleted (as it should be).

[Walter Roberson]

Which workspace are you looking at? clear is going to remove from the current workspace, and functions have their own workspace. I speculate that you might be attempting to clear from the base workspace. If so then you need to use

evalin('base', 'clear varname');

[Matt]

You are correct, I am trying to remove that variable from the base workspace. However, I do not understand where I should put that command line. Could you elaborate your idea?

[Titus Edelhofer]

Hi Matt,

the evalin instructs MATLAB to evaluate the string in another workspace (usually the base workspace). So the line that Walter wrote can be called basically anywhere you like, it will always do the same and clears the variable varname from the base workspace ...

Titus

[Titus Edelhofer]

And you were right, you should have used the () ...

[Matt]

Thank you for your answer guys. I am still struggling on this simple task however. I've tried several combination and eventho I understand the principle of evalin and assignin, I cannot get my head around this.

varname=strcat('time',num2str(get(popupmenu1, 'Value')))
evalin('base', varname)
clear varname

The first line should give me something like time1, time2, or time3. I am then getting the value out of the workspace with evalin, and then clearing it, but it doesn't work.

[Titus Edelhofer]

As I wrote below, this should work

varname=strcat('time',num2str(get(popupmenu1, 'Value')))
% get the data from base workspace
data =evalin('base', varname);
% clear the variable
evalin('base', ['clear ' varname]);

Answer 2

[Titus Edelhofer]

You can either use clear as function as you did, or use string concatenation. Since you need to use evalin anyway, string concatenation is not as bad as usual:

Summarizing, adding the following line after

varname=strcat(...)

should do:

evalin('base', ['clear ' varname]);

Titus