I have a cell array where each cell contains a matrix (different sizes). I would like, e.g., to take all the second columns of the matrices providing a command like:
aux = cArray{:}(:,2)
The result I'd like to obtain is a cell array where each cell contains the second column of the original matrix, but the command doesn't work (and I can even see why, since the output of cArray{:} is not a matrix ... )
Is there a compact command to get what I want instead of a cycle filling up the cell array ?
The reason why it doesn't work is that indexing a cell array with {:} produces a comma-separated list, which is not indexable anymore. You can view it as the "unwrapped" contents of the cell array separated by commas.
You can achieve what you want with cellfun:
result = cellfun(#(x) x(:,2), cArray, 'uniformoutput', false);
This applies the anonymous function #(x) x(:,2) to each cell's contents, and packs the results in a cell array.
Related
I have a column matrix and a cell array which has two columns.The first column has 1x2 doubles and the second column has 1x1 doubles.
For example
columnMatrix = [1;5];
cellArray = {[1,8],[10];[8,1],[20];[4,6],[80];[3,5],[40];[14,16],[85];[5,10],[36]};
I would like to search each element of columnMatrix in cellArray(:,1) and then return its corresponding value in cellArray(:,2)
For example the output has to be like this
newCell = {[1],[10,20];[5],[40,36]};
I tried using the ismember function in this way
[~,idx] = ismember(cell2mat(cellArray(:,1)),columnMatrix (: , 1));
This returns all the indices which have the searched element but they are in two seperate columns and I can not perform any other logical operation to get the corresponding second column entry.
Is there some way this operation can be achieved? Could some one please help?
Thanks
First of all, convert first column of cellArray to a matrix so it would be easier to search values in. Then iterate over columnMatrix values (e.g. using arrayfun, but you could also use for loop), find rows that match (any across columns) and select corresponding values from the second column of cellArray, converting to numeric array ([cellArray{...,2}]). Finally, append the columnMatrix as the first column of the resulting cell array:
columnMatrix = [1;5]; cellArray = {[1,8],[10];[8,1],[20];[4,6],[80];[3,5],[40];[14,16],[85];[5,10],[36]};
mat = cell2mat(cellArray(:,1));
values = arrayfun(#(x) [cellArray{any(mat==x,2),2}], columnMatrix, 'uni', false);
result = [num2cell(columnMatrix), values];
In MATLAB, have an N-dimensional cell C, where N is an integer only determined at runtime. How do I access a specific element of C with a vector variable id? For example, with N=3 and id=[1,5,2], how to programmatically get the content of c{1,5,2}? I cannot hard-code it as c{id(1),id(2),id(3)} since N is only fixed at runtime.
If id is a cell array, then you can use sub2ind for this by taking advantage of the comma separated list syntax ,i.e. {:}, to send a variable number of inputs to sub2ind
id = {1,5,2};
ind = sub2ind(size(C), id{:})
c{ind}
if id isn't a cell array (and for some reason can't be created as one), then use num2cell to convert it.
I would like to covert three <1xN cell> (A, B and C) into a single Nx3 matrix. Could someone help me with this?
C={{1xN}; {1xN}; {1xN}};
where each N is a number in single quotes, e.g.
C = {{'123123' ,'12324', ....N times}; {'123123', '12324', ....N times}; {'123123', '12324' ,....N times}}
Since a couple of them mentioned about the ridiculous input, this is the reason for having it in the above form.
The three nested array of cells are the results of a regexp where my string and expression are both strings. Therefore I have the output of regexp as three cell arrays of row vectors.
For e.g.
node_ids=regexp(nodes,'(?<=node id=")\d*','match');
I can use cat function and then use a str2double for all three cell arrays and finally form a matrix by cell2mat.
For e.g.
node_ids=cat(1,node_ids{:});node_ids=str2double(node_ids);
But this takes more time and has more LOC.
My question is can it be done with fewer lines of code?
I tried using the cat function but keep getting this error:
Cannot support cell arrays containing cell arrays or objects.
Your input data is pretty bad.... why are you using a nested array of cells where each element is a string?
In any case, assuming C is your original input data, do this:
C = {{'123123' '12324'}; {'123123' '12324'}; {'123123' '12324'}};
out = cellfun(#(x) cellfun(#str2num, x, 'uni', 0), C, 'uni', 0);
out = cell2mat(cellfun(#cell2mat, out, 'uni', 0));
First line is some dummy data. Next line first goes through every nested cell element over your cell array and converts the strings into numbers. However, these are still in cell arrays. As such, the next line converts each cell array in the nested cell into a matrix, then we merge all of the cells together into one final matrix.
We get:
>> out
out =
123123 12324
123123 12324
123123 12324
I get a cell array which contains 103 cells of different dimensions. Each cell of my cell array represents a matrix and it can be displayed as an image. How can I extract each cell (ie each matrix) in a for loop?
I know how to do that one by one but not for the whole cell :
image1 = cellArray{1}; % extract matrix 1 (on 103) from the cell array #1
image2 = cellArray{2}; % and so on
Thanks for your help
The easiest way to loop through your cell array and apply to same function to every cell is to use cellfun. If your function returns a scalar e.g.
f = #(x)max(:)
then it's as simple as
cellfun(f, cellArray)
Note that f above is an anonymous function (or rather a function handle to an anonymous function), but more likely your function will be in its own m-file in which case you need to use the # operator:
cellfun(#f, cellArray)
Lastly, if your output is not a scalar then call
cellfun(#f, cellArray, 'uni' 0)
I have a cell array (A) with size of 400 x 1 and each cell of this array includes a matrix with size 9 x 4. As such, it looks like this:
A={[9x4 double];[9x4 double];...;[9x4 double]};
Now, I want to remove the zero rows from these sub matrices and then obtain a new A cell array called A_new where its sub matrices don't have any zero rows like this:
A_new={[5x4 double];[7x4 double];...;[4x4 double]};
By my below code, I can find the index of rows which are not zero but I couldn't create my cell array like I mentioned above. This is my written code and for the bold part, I have a problem and I couldn't solve it.
for i=1:A_Length
[row,col]=find(A{i,1});
out=[row col];
NNZ_row=unique(row);
Length_NNZ= length(NNZ_row);
for j=1:Length_NNZ
**A_NonZero{i,1}= ??????????**
end
end
What I would do is take each cell, then use all on the opposite of the matrix over all of the columns in each row to determine which rows contain all zeroes. Once you do this, use these locations and remove those rows from this matrix and save this to your new matrix.
As such, do this:
A_new = cell(1,numel(A));
for i=1:numel(A)
mat = A{i};
ind = all(~mat, 2);
A_new{i} = mat(~ind,:);
end
The first line of code creates a new cell array that is the same size as A. Next, for each element in A, extract the matrix at each cell location, use all on the opposite of this matrix to find those elements that we need to keep, then save this new matrix into the corresponding location in A_new.
If you want to do this in a single line of code, use cellfun:
A_new = cellfun(#(x) x(~all(~x,2),:), A, 'uni', 0);
The first argument to cellfun is an anonymous function that performs what the for loop was doing. We find those rows that contain all zeroes and use those to remove the rows in each matrix in the cell array. The second argument is the matrix we want to operate on, which is A. The 'uni' and 0 flags are important because the outputs are not single values but matrices, and so the output of this function will be a cell array that is the same size as A where each element is the matrix for those corresponding locations in A with the zero rows removed.
You should use a combination of cellfun and any:
A_new = cellfun(#(x) x(any(x~=0,2),:), A, 'UniformOutput', false);
should do the trick.