remove all strings from nested cell array

Hi,

I'm trying to remove all string/chars from a 4x10 cell array where each cell in the array contains a 40x1 column vector (so as you can see, it's nested). Most commands I usually use such as cell2mat don't work on this because the cell array is nested.

Or, if preferred, is there a way to read in all the elements of a certain column in one of the cells in a cell array apart from the elements containing strings? e.g:

col=rand(4,10) %matrix containing column indices
for i=1:4
    for j=1:10
        new_cell_arrray{i,j}=g{i,1}(:,col(i,j)); %g is another (existing) 4x1 cell array and new_cell_array is 4x10.
    end
end

Thank you

[Walter Roberson]

If you "remove" an entry from a 2D array, the result cannot be a 2D array any more.

Answer 1

[Walter Roberson]

C = num2cell(randi(9,4,10));
C(randperm(numel(C), 4)) = {"string"};
C(randperm(numel(C), 4)) = {'chars'};

C

C = 4×10 cell array
    {[5]}    {[       8]}    {[5]}    {[6]}    {[1]}    {[       8]}    {'chars'}    {'chars'   }    {["string"]}    {'chars'}
    {[3]}    {["string"]}    {[4]}    {[1]}    {[2]}    {["string"]}    {[    1]}    {[       9]}    {[       5]}    {[    8]}
    {[8]}    {[       5]}    {[4]}    {[8]}    {[9]}    {[       2]}    {[    1]}    {[       5]}    {[       6]}    {[    7]}
    {[3]}    {[       3]}    {[5]}    {[1]}    {[5]}    {[       2]}    {'chars'}    {["string"]}    {[       9]}    {[    8]}

for K = 1 : size(C,2)
    mask = ~cellfun(@(c)ischar(c)||isstring(c), C(:,K));
    subset{K} = C(mask, K);
end
subset

subset = 1×10 cell array
    {4×1 cell}    {3×1 cell}    {4×1 cell}    {4×1 cell}    {4×1 cell}    {3×1 cell}    {2×1 cell}    {2×1 cell}    {3×1 cell}    {3×1 cell}

subset{1}, subset{2}

ans = 4×1 cell array
    {[5]}
    {[3]}
    {[8]}
    {[3]}

ans = 3×1 cell array
    {[8]}
    {[5]}
    {[3]}

[Davindra Usov]

Thank you so much for your response, it was very helpful! Can i ask how this could be modified in a case where each cell in the 4x10 array contains a 1x40 array that has both chars and numbers, rather than just chars only. I'm looking to eliminate just the char parts of the cells, rather than the entire cells themselves.

[Walter Roberson]

for J = 1 : 4
    for K = 1 : 10
        thiscell = num2cell(randi(9, 40, 1));
        if rand() > 0.3; thiscell{randi(40)} = 'characters'; end
        if rand() > 0.3; thiscell{randi(40)} = "string"; end
        C{J,K} = thiscell;
    end
end
whos C

  Name      Size             Bytes  Class    Attributes

  C         4x10            187802  cell               

C{1}

ans = 40×1 cell array
    {[         7]}
    {[         5]}
    {[         2]}
    {[         7]}
    {[         9]}
    {["string"  ]}
    {[         8]}
    {[         2]}
    {[         1]}
    {'characters'}
    {[         7]}
    {[         8]}
    {[         5]}
    {[         5]}
    {[         7]}
    {[         8]}

subset = cell(size(C));
for J = 1 : numel(C)
    mask = ~cellfun(@(c)ischar(c)||isstring(c), C{J});
    subset{J} = C{J}(mask);
end

whos subset

  Name        Size             Bytes  Class    Attributes

  subset      4x10            177088  cell               

subset{1}

ans = 38×1 cell array
    {[7]}
    {[5]}
    {[2]}
    {[7]}
    {[9]}
    {[8]}
    {[2]}
    {[1]}
    {[7]}
    {[8]}
    {[5]}
    {[5]}
    {[7]}
    {[8]}
    {[4]}
    {[1]}

[Davindra Usov]

Thanks again for your help, it is much appreciated! the code is giving me an empty cell array for subset. In each cell, I have 4 strings and 36 numbers. I think this is why I'm getting an empty array, because each cell contains at least one string? I would paste my code but the amount of info I'm allowed to ask is what I've posted on this forum, unfortunately I'm not allowed to post the code itself as it is my coursework :(

[Walter Roberson]

"In each cell, I have 4 strings and 36 numbers."

Okay, I will generate 4 strings and 36 numbers per cell.

for J = 1 : 4
    for K = 1 : 10
        thiscell = num2cell(randi(9, 40, 1));
        rp = randperm(40,4);
        thiscell(rp) = {"string"};
        C{J,K} = thiscell;
    end
end
whos C

  Name      Size             Bytes  Class    Attributes

  C         4x10            206080  cell               

C{1}

ans = 40×1 cell array
    {[       4]}
    {[       1]}
    {[       4]}
    {[       4]}
    {[       1]}
    {[       3]}
    {[       1]}
    {[       6]}
    {[       4]}
    {["string"]}
    {[       4]}
    {[       7]}
    {["string"]}
    {[       1]}
    {[       3]}
    {[       5]}

subset = cell(size(C));
for J = 1 : numel(C)
    mask = ~cellfun(@(c)ischar(c)||isstring(c), C{J});
    subset{J} = C{J}(mask);
end

whos subset

  Name        Size             Bytes  Class    Attributes

  subset      4x10            165440  cell               

subset{1}

ans = 36×1 cell array
    {[4]}
    {[1]}
    {[4]}
    {[4]}
    {[1]}
    {[3]}
    {[1]}
    {[6]}
    {[4]}
    {[4]}
    {[7]}
    {[1]}
    {[3]}
    {[5]}
    {[5]}
    {[5]}

and see that after the filtering, there are 36 entries left. All of the string() objects and character vectors have been removed.

[Davindra Usov]

Thank you so much! it worked :D