Thread Subject: Writing to Cells

Dear All,

I'm trying to alter the contents of an array of cells. I thought that something like

a = {2:5}'
b = {3:6}'
a{2:end, 1} = b{2:end, 1}

would accomplish such a task, but it doesn't. Can someone please explain where I'm going wrong?

"james bejon" <jamesbejon@yahoo.co.uk> wrote in message <hnolpf$4uq$1@fred.mathworks.com>...
> Dear All,
>
> I'm trying to alter the contents of an array of cells. I thought that something like
>
> a = {2:5}'
> b = {3:6}'
> a{2:end, 1} = b{2:end, 1}
>
> would accomplish such a task, but it doesn't. Can someone please explain where I'm going wrong?

one of the solutions

     a={(2:5).'}; % <- note proper use of TRANSPOSE...
     b={(3:6).'};
     a{1}(2:end,1)=b{1}(2:end,1);
     a{1}
%{
% ans =
     2
     4
     5
     6
%}

us

I see. Thanks. By the way, why is this use of transpose 'proper'? I've seen other people use it, but it seemed a bit counter-intuitive to me.

"james bejon" <jamesbejon@yahoo.co.uk> wrote in message <hnouf2$jdc$1@fred.mathworks.com>...
> I see. Thanks. By the way, why is this use of transpose 'proper'? I've seen other people use it, but it seemed a bit counter-intuitive to me.

well... let's see...

% since you wrote
     a={2:5}'
% the assumption was that you wanted to create a CELL, which contains a COL vec
% above syntax does NOT achieve this... as a matter of fact, it does NOT do
% anything because the transpose of a 1x1 CELL is... a 1x1 CELL
     [size(a);size(a.')]
%{
% ans =
     1 1
     1 1
%}
% and
     a{:}
% ans = 2 3 4 5 % <- still a (default) ROW vec
% now,
     a={(2:5).'};
     a{:}
%{
% ans = % <- a COL vec
     2
     3
     4
     5
%}

just a thought...
us

Thanks. I'm still struggling a bit with this though. Suppose I've imported some text data from an Excel spreadsheet. It's come in as, say, a 20 x 10 cell. Now, how do I copy, say, the 5th column to the 4th column, or everything from the 3rd cell down in the 5th column to their equivalents in the 4th column? I'm obviously not understanding the syntax here.

"james bejon" <jamesbejon@yahoo.co.uk> wrote in message
news:hnp1a9$sqh$1@fred.mathworks.com...
> Thanks. I'm still struggling a bit with this though. Suppose I've
> imported some text data from an Excel spreadsheet. It's come in as, say,
> a 20 x 10 cell. Now, how do I copy, say, the 5th column to the 4th
> column, or everything from the 3rd cell down in the 5th column to their
> equivalents in the 4th column? I'm obviously not understanding the syntax
> here.

Indexing into a cell array with parentheses () operates on the cells in the
cell array.
Indexing into a cell array with curly braces {} operates on _the contents
of_ the cells in the cell array.

C = cell(5, 3);% using a smaller example for demonstration
for k = 1:numel(C)
    C{k} = k; % Since this uses {}, we're assigning to the _contents_ of the
kth cell
    C(k) = {k}; % or we can assign a cell as the kth cell using ()
end
C % Just for display purposes

C(:, 2) = C(:, 3) % copying the CELLS from the 3rd column into the CELLS in
the 2nd column
% or
[C{:, 1}] = C{:, 3} % copy the _contents_ of the cells from the 3rd column
into the _contents_ of the cells in the 1st column

The latter example may take you a little bit of time to understand, and I
think we only made it work without DEAL a few (4 or 5) releases ago. For an
explanation, look at the following page from the documentation that talks
about comma-separated lists:

http://www.mathworks.com/access/helpdesk/help/techdoc/matlab_prog/br2js35-1.html

--
Steve Lord
slord@mathworks.com
comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ

Thanks Steve. That's a really helpful response.