Add a zero element to the beginning of each existing cell array

Question

NA 2019-1-18

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/440356-add-a-zero-element-to-the-beginning-of-each-existing-cell-array

回答： Image Analyst 2019-1-19

采纳的回答： Stephen23

I have C={[-8;-5],[1;-4;-5;-5;-5],[-3;-5]}

I want to get this result CC={[0;-8;-5],[0;1;-4;-5;-5;-5],[0;-3;-5]}

I use this code, but do not works c = cellfun(@(x)(x(0)==0), a, 'UniformOutput', false);

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Answer 1

Stephen23 2019-1-18

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/440356-add-a-zero-element-to-the-beginning-of-each-existing-cell-array#answer_356944

编辑：Stephen23 2019-1-18

在 MATLAB Online 中打开

cellfun(@(v)[0;v],C,'uni',0)

And checking:

>> C = {[-8;-5],[1;-4;-5;-5;-5],[-3;-5]};
>> CC = cellfun(@(v)[0;v],C,'uni',0);
>> CC{:}
ans =
   0
  -8
  -5
ans =
   0
   1
  -4
  -5
  -5
  -5
ans =
   0
  -3
  -5

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Stephen23 2019-1-18

编辑：Stephen23 2019-1-18

@Naime Ahmadi: please explain these four lines, they are not clear to me:

CC{1}(index2)=0      B(2)=-5.1         0-5.1=-5.1
CC{1}(index3)=-8     B(3)=-12.2      -8-5.1=-13.1
CC{1}(index4)=-5     B(4)=-10         -10-5.1=-15.1
5.1 changes for CC{2}

You write that for the first line:

CC{1}(index2)=0 B(2)=-5.1 from 0 it changes to -5.1 0-5.1=-5.1

Then why is the second line not?:

CC{1}(index3)=-8 B(3)=-12.2 from -8 it changes to -20.2 -8-12.2=-20.2

What are index2, index3, and index4? You do not define them anywhere, nor do they seem to be required to get those values from CC.

EDIT: Your previous three comments seem to give different algorithms. It is even less clear which, if any, of these comments correctly clarifies what you are trying to do. Here you wrote

CC{2}(index11)=-5     B(11)=-15.1          -5-10.1=-15.1
%              -5           -15.1   <->    -5      -15.1

whereas here you wrote:

CC{1}(index4)=-5     B(4)=-10         -10-5.1=-15.1
%             -5          -10   <?>   ???     ?????
%                                      -5     -10   following above example.

Stephen23 2019-1-19

编辑：Stephen23 2019-1-19

Lets split this line:

tmp = cellfun(@(c,i)c+B(i(1)),CC,index,'uni',0);

into two lines:

fun = @(c,i)c+B(i(1));
tmp = cellfun(fun,CC,index,'uni',0);

where the first line defines an anonymous function:

https://www.mathworks.com/help/matlab/matlab_prog/anonymous-functions.html

For each of the corresponding cell contents in CC and index, that anonymous function will calculate

c+B(i(1))

where c and i are the function inputs, as provided by cellfun, i.e. are the cell contents of CC and index. So this is equivalent to:

CC{1}+B(index{1}(1))
CC{2}+B(index{2}(1))
CC{3}+B(index{3}(1))
... etc.

NA 2019-1-19

Thank you so much.

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Answer 2

Image Analyst 2019-1-19

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/440356-add-a-zero-element-to-the-beginning-of-each-existing-cell-array#answer_357141

在 MATLAB Online 中打开

Granted, cellfun() is a bit cryptic, so if you want a simple, easy to understand intuitive method, just use for loops:

C = {[-8;-5],[1;-4;-5;-5;-5],[-3;-5]};
for col = 1 : size(C, 2)
	for row = 1 : size(C, 1)
		existingContents = C{row, col}; % Get existing vector
		C{row, col} = [0; existingContents]; % Prepend 0
	end
end
celldisp(C)