how to make a variable name from a string

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2013a version
>> test='eye'
>> value = [5,5,3]
value =
5 5 3
>> eval([sprintf(test) '= data+1']);
Index exceeds matrix dimensions.
How to fix this error? Thank you for helping!

Accepted Answer

kjetil87
kjetil87 on 16 Aug 2013
Edited: kjetil87 on 16 Aug 2013
The error should not appear, your code looks to work exept for the part of 'data' , should this instead be value?
test='eye';
value=[1,2,3];
eval([sprintf(test) '=value+1'])
eye =
2 3 4
The index exceeds matrix dimension could be related to that you have at some point declared a variable in your workspace ( or funciton or whatever ) with the name of eval.
try typing
which eval
it should return that eval is a built-in function, if it returns eval is a variable there is the reason for your error. If so just use
clear eval
  2 Comments
xianghong
xianghong on 19 Aug 2013
when I tried this morning, it worked! Thank you so much! Have a great week!
Xianghong

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More Answers (3)

Walter Roberson
Walter Roberson on 16 Aug 2013

xianghong
xianghong on 16 Aug 2013
This seems like to name the fields within a variable. If I just want to make a variable name from a string, how to do it? Thanks!
  1 Comment
Walter Roberson
Walter Roberson on 16 Aug 2013
No, it is not just for creating field names within a variable. It shows a number of different alternatives to creating a variable from a string, recommending strongly that you use one of the alternatives instead of creating a variable dynamically. At the end of the FAQ it shows how to create a variable dynamically, for the rare case when you really need to do that. If you are not engaged in creating extensions to MATLAB itself, chances are that there is a better route than creating a variable dynamically.

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xianghong
xianghong on 16 Aug 2013
EDU>> test='eye';
EDU>> value=[1,2,3];
EDU>> eval([sprintf(test) '=value+1'])
Index exceeds matrix dimensions.
Looks like it still gave the error. What shall I do?
Thanks,
  2 Comments
Walter Roberson
Walter Roberson on 16 Aug 2013
Please use the command
clear eval
and then try again
xianghong
xianghong on 19 Aug 2013
thank you so much! It worked this monday morning!
Have a nice day!
Xianghong

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