Thread Subject: Anonymous function creation from string

Hi

I have a GUI where the user can enter a function (as a
string) that is evaluated in another routine. For example,
the user may enter 'theta(1)*x^2 - theta(2)*x^3'.

Currently I convert the above string expression to an
anonymous function by using EVAL, e.g.
>> fHnd = eval(['@(x,theta) (',str,')'])
where str is the string given in the GUI. Can anyone suggest
a better way of creating the anonymous function without
using eval?

Cheers,
Nick

Hi,

You can directly evaluate the user string as far as all
inputs ("theta", "x"...) are in your current workspace...

For instance,
theta=[2 3];
a=1;

try
  my_result=eval('theta(1)*x^2 - theta(2)*x^3');
catch
  disp('Unable to evaluate user expression')
end

If the user expression is a simple matlab function, you can
then use "str2func" function.

regards, chris

"Nick Denman" <ngdenmanNOSPAM@gmail.REMOVETHIS.com> wrote
in message <frr1de$7a5$1@fred.mathworks.com>...
> Hi
>
> I have a GUI where the user can enter a function (as a
> string) that is evaluated in another routine. For example,
> the user may enter 'theta(1)*x^2 - theta(2)*x^3'.
>
> Currently I convert the above string expression to an
> anonymous function by using EVAL, e.g.
> >> fHnd = eval(['@(x,theta) (',str,')'])
> where str is the string given in the GUI. Can anyone
suggest
> a better way of creating the anonymous function without
> using eval?
>
> Cheers,
> Nick

In article <frr1de$7a5$1@fred.mathworks.com>,
ngdenmanNOSPAM@gmail.REMOVETHIS.com says...
> Hi
>
> I have a GUI where the user can enter a function (as a
> string) that is evaluated in another routine. For example,
> the user may enter 'theta(1)*x^2 - theta(2)*x^3'.
>
> Currently I convert the above string expression to an
> anonymous function by using EVAL, e.g.
> >> fHnd = eval(['@(x,theta) (',str,')'])
> where str is the string given in the GUI. Can anyone suggest
> a better way of creating the anonymous function without
> using eval?
>
> Cheers,
> Nick
>
not sure it will work in your case, but look into str2func.

--
Loren
http://blogs.mathworks.com/loren/