Reading in and Evaluating strings from standalone GUI using appdata

I have been attempting to write a standalone windows GUI for a program that I have. It necessitates that I allow the user to input a string function for a number of items and at some point in the code it executes said strings. The final value of the strings are a function of an array (T) and output an array [item name](j). There is already a string value stored in appdata with the same name (a default in case no user changes are made).

For example.

Default written into program:

setappdata(0,'Item1' , '50.^(-7590/T(j)-7.46)');

In user window, a box with a custom entry such as:

50.^(-150/T(j)+1) and a corresponding GUI code for 

setappdata(0,'Item1',get(handles.edit107,'string'));

where the tag of the text box is edit107

and a subsequent evaluation of

 Item1result(j)=eval(getappdata(0,'Item1'));

Assuming the T and j are both defined properly as arrays.

In the certain situation where a user might enter just a single number (which is realistic).

Is there anyway around the:

Undefined function 'eval' for input arguments of type 'double'.

Answer 1

[Robert Cumming]

Am I correct in assuming the user enters any string which then gets executed in eval? This is NOT advisable.... for example: the user could enter: 'system ( 'delete C:\*' )'

Anyway - to answer your questions: have you seen

try
  do something 
catch  % if it errors - the error is captured
  do something else
end

[Matthew]

Wow I hadn't considered that to be a possibility, yikes, thanks for the heads up. While I'm fairly confident that would never be the case, is there a safer evaluation method?

I also hadn't previously been aware of the try function, thank you!

Answer 2

[Matthew]

On this same note, is there any simpler way to check if the input is a number and if it isn't assume that it is a string and evaluate?

Ex:

    if isnumeric(getappdata(0,'Item1'))

      Item1R=getappdata(0,'Item1');

    else

      Item1R=eval(getappdata(0,'Item1'));

    end

If there is no way for the eval function to process a number by itself (or an alternative function) then i need to do the above for about 150 some items...

[Robert Cumming]

You should add this to your original question - since it builds on your question - but yes isnumeric is a satisfactory way of checking if a variable is a number.

Perhaps if you expalin your aim in more detail you might get more help on avoiding eval.

Have you seen this link on avoiding eval?