Struct name from variable in Matlab

Question

I have created a structure containing a few different fields. The fields contain data from a number of different subjects/participants.

At the beginning of the script I prompt the user to enter the "Subject number" like so:

 prompt='Enter the subject number in the format SUB_n: ';
 SUB=input(prompt,'s');

Example SUB_34 for the 34th subject.

I want to then name my structure such that it contains this string... i.e. I want the name of my structure to be SUB_34, e.g. SUB_34.field1. But I don't know how to do this.

I know that you can assign strings to a specific field name for example for structure S if I want field1 to be called z then

S=struct;
field1='z';
S.(field1);

works but it does not work for the structure name.

Can anyone help?

Thanks

one option would be using eval although is not a good programming practice: eval([SUB ' = struct']) will create a struct variable whose name is the content of SUB. — user2261062
– user2261062, Commented Jul 19, 2016 at 15:09

Suever · Accepted Answer · 2016-07-19 15:48:30Z

7

Rather than creating structures named SUB_34 I would strongly recommend just using an array of structures instead and having the user simply input the subject number.

number = input('Subject Number')
S(number) = data_struct

Then you could simply find it again using:

subject = S(number);

If you really insist on it, you could use the method proposed in the comment by @Sembei using eval to get the struct. You really should not do this though

S = eval([SUB, ';']);

Or to set the structure

eval([SUB, ' = mydata;']);

One (of many) reasons not to do this is that I could enter the following at your prompt:

>> prompt = 'Enter the subject number in the format SUB_n: ';
>> SUB = input(prompt, 's');
>> eval([SUB, ' = mydata;']);

And I enter:

clear all; SUB_34

This would have the unforeseen consequence that it would remove all of your data since eval evaluates the input string as a command. Using eval on user input assumes that the user is never going to ever write something malformed or malicious, accidentally or otherwise.

edited Jul 19, 2016 at 15:48

answered Jul 19, 2016 at 15:10

Suever

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