trouble with the eval function and cell

Hi guys,

AIM OF FUNCTION

First I need to read out ~100 .mat files with preprocessed data, each containing around 50 variables, a wild mixture of matrices, stings and structs. No problem so far. I then want to store all variables from a file in a cell array.

Example:

load processeddata3.mat
varList = who;
for i=1:+1:size(varList,1)
  s = ['data{ex.no,1}.' varList(i) ' = ' varList(i)]
  eval(s)
end

where data is the name of the cell array I wish to create, ex.no is the interal number of a dataset.

The string looks like that:

s = 'data{ex.no}.'    'AfterSpikes'    ' = '    'AfterSpikes'

If I type it in by hand it works perferctly, eval gives the error message

??? Undefined function or method 'eval' for input arguments of type 'cell'.

Any idea how to solve this, or an idea for a workaround? Help would really be appreciated.

Thanks, Alex

Answer 1

[Andrew Newell]

Avoid eval - use dynamic field names:

data{ex.no,1}.(varList{i}) = varList{i};

See "Generate Field Names from Variables" in Structures.

A simpler approach is to use

s = load('processeddata3.mat');

EDIT: Modified in view of Walter's comment and discussion below

[Alex R. Crowan]

Thanks, this is a good tip and I will keep it in mind for the next bit of code I have to write, looks neater than what I did so far for data organisation. Didn't know that worked for structs, and now I wonder what cells are good for, anyway? I hate the curly brackets

Unfortunately, it doesn't quite solve my problem.

The dynamic field name assignment works nice, but the the second part, ' = varList(i);', just assigns the string from varList to the new variable, and not the variable of that name, which was the aim in the first place.

data{ex.no,1}.(varList(i)) = eval(varList(i));

doesn't work either, because my datasets contain cells, too... Unless there is some other trick I'll probably have to put in the 50 variable names myself, could be worse.

Thanks for the answer and have a nice weekend!

[Andrew Newell]

Oh! You can do that in a single command:

S = load('processeddata3.mat');

As for cells, one nice use for them is to store an array of strings of different lengths - and see also varargin.

Answer 2

[Walter Roberson]

varList{i} not varList(i)