Check appearance counts of multiple patters in a cell matrix

Question

Yi-xiao Liu 2020-1-8

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/499475-check-appearance-counts-of-multiple-patters-in-a-cell-matrix

评论： Guillaume 2020-1-9

I have 2 cell matrixs:

A =
  m×1 cell array
    {'abc'}
    {'def'}
    {'123'}
    ......
B =
  n×1 cell array
    {'abcsafadefs2'}
    {'dsabcdsdef11'}
    {'abcssp123'}
    ......

I want a output matrix of whether patterns in A has appear 7 times in B:

C =
  m×1 logical array
    {true}
    {true}
    {false}
    ......

So in this example pattern "abc" have matches in exactaly 7 elements in B, so does "def", but not "123".

I now do this with a for loop

for i=1:length(A)
    C(i)= (nnz(contains({B}, A(i)))==7);
end

Any way to vectorize the code?

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Answer 1

Guillaume 2020-1-8

1
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https://ww2.mathworks.cn/matlabcentral/answers/499475-check-appearance-counts-of-multiple-patters-in-a-cell-matrix#answer_409251

在 MATLAB Online 中打开

Any way to vectorize the code?

Not really, you could cellfun it, but that's not vectorisation (cellfun is just a loop in disguise):

C = cellfun(@(a) nnz(contains(B, a)) == 7, A);

Note that if you use a loop, you should preallocate the output:

C = false(size(A));
for i = 1:numel(A)
    C(i) = ...
end

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Yi-xiao Liu 2020-1-8

编辑：Yi-xiao Liu 2020-1-8

Can you explain more on the example? I find myself having hard time understanding it, though it does work

Guillaume 2020-1-9

在 MATLAB Online 中打开

cellfun(fun, A) applies the function fun to each element of A. Here, fun is the anonymous function:

@(a) nnz(contains(B, a)) == 7

which written as normal function would be equivalent to:

function out = anonymous_function(a)
    %unlike normal functions, anonymous functions can capture variables in the enclosing function
    %so B is in scope in the anonymous function
    out = nnz(contains(B, a)) == 7;
end

which is basically the code you had originally.

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