MATLAB Central Newsreader - cell arrays and structs

cell arrays and structs

David — Sun, 09 Aug 2009 10:38:58 -0400

I have a 380x1 cell array fPN. Each cell has class 'char' and contains
a string.
I also have a 380x1 cell array ta. Each cell has class 'struct'. For
example I get

>> ta{5}

ans =

        num: '1'
       cond: 'CANCER'
         vf: '1'
    protein: 'CEA_01'

My question is: Is there an array method to add to each ta{i} a new
field whose value will be the string in fPN{i}, or should I just give
up and loop through the cells, adding the new field one by one?

Thanks
David

Re: cell arrays and structs

Oleg Komarov — Sun, 09 Aug 2009 11:09:02 -0400

David <david.b.a.epstein@googlemail.com> wrote in message <a2f1b899-3886-492b-adb0-9530210f6315@g19g2000vbi.googlegroups.com>...
> I have a 380x1 cell array fPN. Each cell has class 'char' and contains
> a string.
> I also have a 380x1 cell array ta. Each cell has class 'struct'. For
> example I get
>
> >> ta{5}
>
> ans =
>
> num: '1'
> cond: 'CANCER'
> vf: '1'
> protein: 'CEA_01'
>
> My question is: Is there an array method to add to each ta{i} a new
> field whose value will be the string in fPN{i}, or should I just give
> up and loop through the cells, adding the new field one by one?
>
> Thanks
> David

All i can think of is:

% building my example
fPN = cellstr(['example1';'example2']);
ta{1} = struct('num', 1, 'cond', 'CANCER', 'vf', 1, 'protein', 'CEA_01');
ta{2} = struct('num', 1, 'cond', 'CANCER', 'vf', 1, 'protein', 'CEA_01');

% solution 1
Temp = cellfun(@(x) struct2cell(x), ta, 'un',0);
Temp = [Temp{:}]; Temp(end+1,:) = fPN;
ta = cell2struct(Temp, {'num', 'cond', 'vf', 'protein', 'newfield'});

in this case "ta" becomes a 2x1 struct (not a cell anymore).

Otherways u can do a simple loop:
% solution 2
for i = 1:length(ta)
ta{i}.newfield = fPN{i};
end

Re: cell arrays and structs

Doug Schwarz — Sun, 09 Aug 2009 12:40:24 -0400

In article
<a2f1b899-3886-492b-adb0-9530210f6315@g19g2000vbi.googlegroups.com>,
David <david.b.a.epstein@googlemail.com> wrote:

> I have a 380x1 cell array fPN. Each cell has class 'char' and contains
> a string.
> I also have a 380x1 cell array ta. Each cell has class 'struct'. For
> example I get
>
> >> ta{5}
>
> ans =
>
> num: '1'
> cond: 'CANCER'
> vf: '1'
> protein: 'CEA_01'
>
> My question is: Is there an array method to add to each ta{i} a new
> field whose value will be the string in fPN{i}, or should I just give
> up and loop through the cells, adding the new field one by one?
>
> Thanks
> David

Yes, suppose you want to use the field name 'string', then

[ta.string] = fPN{:};

will do it if your version of MATLAB is new enough.

--
Doug Schwarz
dmschwarz&ieee,org
Make obvious changes to get real email address.

Re: cell arrays and structs

Matt — Sun, 09 Aug 2009 15:20:02 -0400

Doug Schwarz <see@sig.for.address.edu> wrote in message <see-82000A.08402409082009@news.frontiernet.net>...

> Yes, suppose you want to use the field name 'string', then
>
> [ta.string] = fPN{:};
>
> will do it if your version of MATLAB is new enough.
>

Of if not, then the following should work for older versions

[ta(1:length(fpN)).string] = deal(fPN{:});

Re: cell arrays and structs

us — Sun, 09 Aug 2009 16:38:01 -0400

Doug Schwarz <see@sig.for.address.edu> wrote in message <see-82000A.08402409082009@news.frontiernet.net>...
> In article
> <a2f1b899-3886-492b-adb0-9530210f6315@g19g2000vbi.googlegroups.com>,
> David <david.b.a.epstein@googlemail.com> wrote:
> > I have a 380x1 cell array fPN. Each cell has class 'char' and contains
> > a string.
> > I also have a 380x1 cell array ta. Each cell has class 'struct'. For
> > example I get
> > >> ta{5}
> > ans =
> > num: '1'
> > My question is: Is there an array method to add to each ta{i} a new
> > field whose value will be the string in fPN{i}, or should I just give
> > up and loop through the cells, adding the new field one by one?

> Yes, suppose you want to use the field name 'string', then
> [ta.string] = fPN{:};
> will do it if your version of MATLAB is new enough.

no - does not work...
according to the OP's spec, his/her TAs are CELLs of STRUCTs - and not just STRUCTs...
hence, a simple for loop is probably the fastest solution...

us

Re: cell arrays and structs

Matt — Sun, 09 Aug 2009 17:02:01 -0400

David <david.b.a.epstein@googlemail.com> wrote in message <a2f1b899-3886-492b-adb0-9530210f6315@g19g2000vbi.googlegroups.com>...

> I also have a 380x1 cell array ta. Each cell has class 'struct'. For
> example I get
>
> >> ta{5}
>
> ans =
>
> num: '1'
> cond: 'CANCER'
> vf: '1'
> protein: 'CEA_01'

This seems like a bad way to store data. Why not use a struct array

sta=[ta{:}];

instead of burying each struct inside a cell where it is harder to get at?

Re: cell arrays and structs

Doug Schwarz — Sun, 09 Aug 2009 18:05:09 -0400

In article <h5mu19$lof$1@fred.mathworks.com>,
"us " <us@neurol.unizh.ch> wrote:

> Doug Schwarz <see@sig.for.address.edu> wrote in message
> <see-82000A.08402409082009@news.frontiernet.net>...
> > In article
> > <a2f1b899-3886-492b-adb0-9530210f6315@g19g2000vbi.googlegroups.com>,
> > David <david.b.a.epstein@googlemail.com> wrote:
> > > I have a 380x1 cell array fPN. Each cell has class 'char' and contains
> > > a string.
> > > I also have a 380x1 cell array ta. Each cell has class 'struct'. For
> > > example I get
> > > >> ta{5}
> > > ans =
> > > num: '1'
> > > My question is: Is there an array method to add to each ta{i} a new
> > > field whose value will be the string in fPN{i}, or should I just give
> > > up and loop through the cells, adding the new field one by one?
>
> > Yes, suppose you want to use the field name 'string', then
> > [ta.string] = fPN{:};
> > will do it if your version of MATLAB is new enough.
>
> no - does not work...
> according to the OP's spec, his/her TAs are CELLs of STRUCTs - and not just
> STRUCTs...
> hence, a simple for loop is probably the fastest solution...
>
> us

You're right, Urs, I missed that. If each cell in ta is a struct with
the same fields they could be concatenated into a proper struct array
with

  ta2 = [ta{:}];

and then

  [ta2.string] = fPN{:};

would work. Then ta2 could be converted back to a cell array with

  c2 = num2cell(ta2);

if desired. But really it would be better to use ta2.

--
Doug Schwarz
dmschwarz&ieee,org
Make obvious changes to get real email address.

Re: cell arrays and structs

Matt — Sun, 09 Aug 2009 19:02:01 -0400

Doug Schwarz <see@sig.for.address.edu> wrote in message <see-846576.14050809082009@news.frontiernet.net>...
> In article <h5mu19$lof$1@fred.mathworks.com>,
> "us " <us@neurol.unizh.ch> wrote:
>
> > Doug Schwarz <see@sig.for.address.edu> wrote in message
> > <see-82000A.08402409082009@news.frontiernet.net>...
> > > In article
> > > <a2f1b899-3886-492b-adb0-9530210f6315@g19g2000vbi.googlegroups.com>,
> > > David <david.b.a.epstein@googlemail.com> wrote:
> > > > I have a 380x1 cell array fPN. Each cell has class 'char' and contains
> > > > a string.
> > > > I also have a 380x1 cell array ta. Each cell has class 'struct'. For
> > > > example I get
> > > > >> ta{5}
> > > > ans =
> > > > num: '1'
> > > > My question is: Is there an array method to add to each ta{i} a new
> > > > field whose value will be the string in fPN{i}, or should I just give
> > > > up and loop through the cells, adding the new field one by one?
> >
> > > Yes, suppose you want to use the field name 'string', then
> > > [ta.string] = fPN{:};
> > > will do it if your version of MATLAB is new enough.
> >
> > no - does not work...
> > according to the OP's spec, his/her TAs are CELLs of STRUCTs - and not just
> > STRUCTs...
> > hence, a simple for loop is probably the fastest solution...
> >
> > us
>
> You're right, Urs, I missed that. If each cell in ta is a struct with
> the same fields they could be concatenated into a proper struct array
> with
>
> ta2 = [ta{:}];
>
> and then
>
> [ta2.string] = fPN{:};
>
> would work. Then ta2 could be converted back to a cell array with
>
> c2 = num2cell(ta2);
>
> if desired. But really it would be better to use ta2.

Note that this solution doesn't really avoid for-loops. num2cell.m uses for loops internally...

Re: cell arrays and structs

David — Sun, 09 Aug 2009 20:29:56 -0400

On 9 Aug, 18:02, "Matt " <x...@whatever.com> wrote:
> This seems like a bad way to store data. Why not use a struct array
>
> sta=[ta{:}];
>
> instead of burying each struct inside a cell where it is harder to get at?

The reason I have a cell array is that this is what an application of
regexp gave me. I was trying to find my way out of the cell array, but
didn't know how. Thanks everyone for showing me the construction---
this solves my problem.
David