Clear function works in command window but not in script file

2015 8 31
2 个回答
更新时间：2015 9 1
6 次查看（30 天）

0 个投票

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?

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回答（2 个）

Walter Roberson
Walter Roberson 2015-8-31

0 个投票

Leave out the (), just
clear varname

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Matt
Matt 2015-8-31
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
Walter Roberson 2015-8-31
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
Matt 2015-9-1
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
Titus Edelhofer 2015-9-1
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
Titus Edelhofer 2015-9-1
And you were right, you should have used the () ...
Matt
Matt 2015-9-1
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
Titus Edelhofer 2015-9-1
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]);

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Titus Edelhofer
Titus Edelhofer 2015-9-1

0 个投票

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

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