MATLAB Central Newsreader - eval begone!

eval begone!

jay vaughan — Mon, 21 Apr 2008 04:12:02 -0400

Hi,

I've seen many posts on the Matlab newsgroup stating that
eval is evil and should be avoided. Upon attempting to
exorcise my code, I couldn't get rid of one of them...

Essentially I have a variable 'var' which I want to save
within a .mat file but with a name other than 'var'. The
user supplies the name. Here's how I do it now.

var = [1 2 3];
answer = inputdlg('choose a name');
var_name_from_user = answer{1};
eval([var_name_from_user '=var;']);
save('saved_file.mat',var_name_from_user);

Any ideas how to do this without eval? It's probably easy
but I just can't see it.

Thanks,
J

Re: eval begone!

roberson@ibd.nrc-cnrc.gc.ca (Walter Roberson) — Mon, 21 Apr 2008 04:16:43 -0400

In article <fuh46i$pav$1@fred.mathworks.com>,
jay vaughan <jvaughan5.nospam@gmail.com> wrote:

>I've seen many posts on the Matlab newsgroup stating that
>eval is evil and should be avoided. Upon attempting to
>exorcise my code, I couldn't get rid of one of them...

>Essentially I have a variable 'var' which I want to save
>within a .mat file but with a name other than 'var'. The
>user supplies the name. Here's how I do it now.

>var = [1 2 3];
>answer = inputdlg('choose a name');
>var_name_from_user = answer{1};
>eval([var_name_from_user '=var;']);
>save('saved_file.mat',var_name_from_user);

>Any ideas how to do this without eval? It's probably easy
>but I just can't see it.

outstruct.(var_name_from_user) = var;
save('saved_file.mat', 'outstruct', '-struct');
--
  "Why does he stagger his mind with the mathematics of the sky?
  Once the question mark has arisen in the human brain the answer must
  be found, if it takes a hundred years. A thousand years."
                                              -- Walter Reisch

Re: eval begone!

jay vaughan — Mon, 21 Apr 2008 04:45:03 -0400

Walter,

Very clever...I like it.

Thanks,

J

P.S. Minor detail...I had to put '-struct' before struct
name 'outstruct' as shown below...

save('saved_file.mat', '-struct', 'outstruct');

roberson@ibd.nrc-cnrc.gc.ca (Walter Roberson) wrote in
message <fuh4fb$743$1@canopus.cc.umanitoba.ca>...
> In article <fuh46i$pav$1@fred.mathworks.com>,
> jay vaughan <jvaughan5.nospam@gmail.com> wrote:
>
> >I've seen many posts on the Matlab newsgroup stating that
> >eval is evil and should be avoided. Upon attempting to
> >exorcise my code, I couldn't get rid of one of them...
>
> >Essentially I have a variable 'var' which I want to save
> >within a .mat file but with a name other than 'var'. The
> >user supplies the name. Here's how I do it now.
>
> >var = [1 2 3];
> >answer = inputdlg('choose a name');
> >var_name_from_user = answer{1};
> >eval([var_name_from_user '=var;']);
> >save('saved_file.mat',var_name_from_user);
>
> >Any ideas how to do this without eval? It's probably easy
> >but I just can't see it.
>
>
> outstruct.(var_name_from_user) = var;
> save('saved_file.mat', 'outstruct', '-struct');
> --
> "Why does he stagger his mind with the mathematics of
the sky?
> Once the question mark has arisen in the human brain the
answer must
> be found, if it takes a hundred years. A thousand years."
> -- Walter Reisch