how to find out the index of a cell array that cell contains my substring?

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Rui Zhang 2024-2-15

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https://ww2.mathworks.cn/matlabcentral/answers/2082653-how-to-find-out-the-index-of-a-cell-array-that-cell-contains-my-substring

评论： Rui Zhang 2024-2-16

采纳的回答： Fangjun Jiang

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My question is:

myCellArray = {'John','Mike','foo'};
substring = 'Jo'

Since myCellArray{1} contains "Jo', I expected the index = 1.

How to use cellfun to find the index of the element(s) in the cell array?

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Rui Zhang 2024-2-15

My Matlab version is 2017b

Rui Zhang 2024-2-15

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If I don't use cell function, the following code should work:

myCellArray = {'John','Mike','foo'};
substring = 'Jo';
indexForMySubstring = zeros([1,numel(myCellArray)]);
kk = 1;
for ii =1: numel(myCellArray)
    if contains(myCellArray{ii},substring)
        indexForMySubstring(kk) = ii;
        kk = kk+1;
    end
end
if kk>1.5
    indexForMySubstring = indexForMySubstring(1:kk-1);
else
    indexForMySubstring = [];
end

This will return array of the indexes that contains 'Jo' in myCellArray

But this code runs too slow when it is used for a large application.

I am looking for a solution that runs faster than this like using cellfun.

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采纳的回答

Fangjun Jiang 2024-2-15

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Do you have to use cellfun()?

myCellArray = {'John','Mike','foo'};
substring = 'Jo'
substring = 'Jo'
find(contains(myCellArray,substring))
ans = 1

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Voss 2024-2-15

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myCellArray = {[],'John','','Mike','foo'};
substring = 'Jo';
% replace non-char entries with empty chars:
fixedCellArray = myCellArray;
fixedCellArray(~cellfun(@ischar,fixedCellArray)) = {''};
myIndex = find(contains(fixedCellArray,substring))
myIndex = 2

Rui Zhang 2024-2-16

Good solution. Thank you!

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Aquatris 2024-2-15

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编辑：Aquatris 2024-2-15

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Using the @Fangjun Jiang example, how about

myCellArray = {'John','Mike','foo','Jonathan','Stuart','Martha','Jo'};
substring = 'Jo';
idx = find(cellfun(@(x) contains(x,substring),myCellArray,'UniformOutput',true))
idx = 1×3
     1     4     7
myCellArray(idx)
ans = 1×3 cell array
    {'John'}    {'Jonathan'}    {'Jo'}

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Aquatris 2024-2-15

编辑：Aquatris 2024-2-16

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Not the cleaness solution but I think you are looking for something like this then:

myCellArray = {[] 'John','Mike',[],'foo','Johanna','Mark',[];...
0 10 11 20 30 40 50 60;...
1 12 13 22 60 70 80 20;...
2 14 15 18 40 20 10 20;...
3 15 20 25 30 40 50 60};
substring = 'Jo';
idx_empty = cellfun(@isempty,myCellArray(1,:)); % find empty cells in first row
myCellArray_Modified = myCellArray(1,:); % create replica of first row of myCellArray
myCellArray_Modified(idx_empty) = {-1}; % replace empty cells with -1 double
idx = find(cellfun(@(x) contains(string(x),substring),myCellArray_Modified(1,:),'UniformOutput',true));
idx % idx is the column numbers of interest
idx = 1×2
     2     6
myCellArray(:,idx)
ans = 5×2 cell array
    {'John'}    {'Johanna'}
    {[  10]}    {[     40]}
    {[  12]}    {[     70]}
    {[  14]}    {[     20]}
    {[  15]}    {[     40]}