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Re: using cellfunction


From: Juan Pablo Carbajal
Subject: Re: using cellfunction
Date: Thu, 11 May 2017 23:47:06 +0200

On Thu, May 11, 2017 at 10:42 PM, BOKU
<address@hidden> wrote:
> Thank you for your response ,
>
> yes I do understand,
>
> but I did already "UniformOutput", false
>
> The problem is the function, as I want to apply a function which needs more
> than just the matrix from the cell x{1,1} (for the first cell), no I need
> furthermore the data which are stored in   x{3,1}  (for the first cell). And
> It seems that I cannot index the matrix. I just dont know what cellfunction
> does with the cell.. I mean if I do @mean or @(x) x-1 i could basicly do
> mean(cell2mat(x)) and it's done! But if i have a {1,3} cell array in which
> {1,1} is a matrix of let's say 300X300X300 and {1,2} is a 1X12 array, and
> {1,3} is a an 200,120 array what happens then. but that is exactly what i
> want to do I want to applay a function to  {1:end,1} with individual datas
> stored in {1:end,3}. And idon't want to loop because it's incredible slow.
> It takes about 20 min looping over this cell and I have several hundreds of
> them. So I want to find another solution.
>
> x{1,i}=foundimfilt{i};
>
> x{2,i}=ref{i};
>
> x{3,i}=meanval{i};
>
>
> function [y]= doit(x)
>
> idxl=x(1,1)(:,:,1)>x(3,1)(7)+0.3 | x(1,1)(:,:,1)<x(3,7)-0.3
>
> x(1,1)(:,:,2)>x(1,3)(6)+0.3 | x(1,1)(:,:,2)<x(1,3)(6)-0.3 ...
>
> &x(1,1)(:,:,3)>x(1,3)(8)+0.3 | x(1,1)(:,:,3)<x(1,3)(8)-0.3;
>
> idxl=imcomplement(idxl);
>
> pointsel=medfilt2(idxl,[10,10]);
>
> endfunction
>
>
> pointselection = cellfun(@doit, x ,"UniformOutput" ,false );
>
>
> On 2017-05-11 22:11, Juan Pablo Carbajal wrote:
>
> On Thu, May 11, 2017 at 9:41 PM, BOKU
> <address@hidden> wrote:
>
> Hello,
>
> I would to apply a function to a 3x371 cell array
>
> so my question would if there is a solution to the following
>
> for i=1:numel(values)                              ####### wrapping elements
> to get access in cellfunktion
> ####### because cellfunction does just deliver the cellaray
>    wrapobj{1,i}=foundimfilt{i};               #######  I hoped that it will
> deliver the 3x1 cell
>    wrapobj{2,i}=ref{i};
>    wrapobj{3,i}=meanval{i};
>
> endfor
>
>
> function [pointsel]= similarpoints(f)
>
>      idxl=f(1,1)(:,:,1)>f(3,1)(7)+0.3 | f(1,1)(:,:,1)<f(3,7)-0.3&
> f(1,1)(:,:,2)>f(1,3)(6)+0.3 | f(1,1)(:,:,2)<f(1,3)(6)-0.3 ...    ####### so
> that i can access the data in the &f(1,1)(:,:,3)>f(1,3)(8)+0.3 |
> f(1,1)(:,:,3)<f(1,3)(8)-0.3; ####### function
>
> idxl=imcomplement(idxl);
> pointsel=medfilt2(idxl,[10,10]);
> endfunction
>
>
> pointselection = cellfun(@similarpoints, wrapobj,"UniformOutput" ,false );
> ############ but unfortunately it seems that i don't
> get the full  cell
>
>
> error: f(7): out of bound 1
> error: called from
>     similarpoints at line 3 column 10
>
>
> is there a solution for the indexing or the delivering the needed
> informations for the function. Basicly i want to apply an individual filter
> to every cell and I need the information stored in wrapobj{3,i} to apply it
> on the matrix stored in wrapobj{1,i}!
>
> wrapobj is a 3x371 cell array.
>
> i would appreciate any help on this
>
> cheers chris
>
>
>
>
> _______________________________________________
> Help-octave mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/help-octave
>
> Hi,
> cellfun respects the size of the input, that is
>
> c = {1,4,7,10;2,5,8,11;3,6,9,12};
> f=@(x) x-1;
> cp = cellfun (f,c)
>
> cp =
>
>     0    3    6    9
>     1    4    7   10
>     2    5    8   11
>
> If you input is a 3x371 cell, then the output of cellfun will be a
> cell of the same size. If the output of the function you evaluate on
> each cell element is an array or cell, then you should tell cellfun
> that 'UniformOutput' is false, e.g.
>
> f=@(x) linspace(1,x,3);
> cp = cellfun (f,c,'UniformOutput', false);
> whos cp
>
> Variables in the current scope:
>
>    Attr Name        Size                     Bytes  Class
>    ==== ====        ====                     =====  =====
>         cp          3x4                        288  cell
>
> Total is 12 elements using 288 bytes
>
>

cellfun, arrayfun and similar functions apply the function to each
element of the cell. so if the function can process all the elements
in the cell, e.g. different sized matrices, scalars, strings, etc..
then cellfun will just apply it to each element. It is the
generalization of the "element-wise" behavior of functions applied to
arrays, i.e. sin, tanh, exp, abs, etc...

But cellfun can also work in two cells, advancing on each other
simultaneously and implement element-wise functions of many inputs
(n-arity), for you case you could do

cellfun (your_func, your_cell(1,:), your_cell(3,:), 'unif', 0)

Does it work?



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