How can I use the find function for cell arrays to search for particular cell vector values

Question

Kevin 2017-3-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/330955-how-can-i-use-the-find-function-for-cell-arrays-to-search-for-particular-cell-vector-values

编辑： Jan 2017-3-27

Suppose I have a cell array:

EC = {[1,2,1,1] [1,3,1,1] [1,4,1,1] [1,1,1,2]}

I need a way to index where the values of the cells = [1,3,1,1] or [1,1,1,2] such that MATLAB returns: [2,4] for the 2nd and 4th cells of array EC.

I've been trying to use the find function, but it doesn't appear you can use that for cell arrays...

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

KSSV 2017-3-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/330955-how-can-i-use-the-find-function-for-cell-arrays-to-search-for-particular-cell-vector-values#answer_259603

在 MATLAB Online 中打开

EC = {[1,2,1,1] [1,3,1,1] [1,4,1,1] [1,1,1,2]} ;
k = {[1,3,1,1] [1,1,1,2]} ;
EC = cell2mat(EC(:)) ;
k = cell2mat(k(:)) ;
[val,idx] = ismember(k,EC,'rows') ;
idx

2 个评论
显示无隐藏无

Kevin 2017-3-27

What does the "val" do? It just seems to be creating a vector of ones corresponding to the length of k (whatever the # of cells I'm looking for), which in this example happens to be 2. How is this ever useful?

Reading help ismember, which calls it LIA (not sure why) says it's just that, an array of same size as 'k', containing true where the elements of 'k' are in 'EC' and false otherwise.

I can understand wanting an index like LOCB (as they call it), and can see how you might just want the number of cases where k is in EC, but how is it useful to just get an array of ones?

Jan 2017-3-27

编辑：Jan 2017-3-27

在 MATLAB Online 中打开

@Kevin: In the general case this command searchs if an element of A occurres in B:

[LIA, LocB] = ismember(A, B);

LIA is a logical index vector related to A (L I A), which is TRUE, if the corresponding element of A occurres in B, while LocB is the index of the matching element of B.

请先登录，再进行评论。

Answer 2

John BG 2017-3-25

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/330955-how-can-i-use-the-find-function-for-cell-arrays-to-search-for-particular-cell-vector-values#answer_260294

在 MATLAB Online 中打开

hi Kevin

the following builds a 2 columns cell where 1st column is just the numeral coinciding with EC amount of elements and 2nd column is variable length indicating what vector of D matches the i-th element of D

EC = {[1,2,1,1] [1,3,1,1] [1,4,1,1] [1,1,1,2]}
D={[1,3,1,1]  [1,1,1,2] }
match={}
for k=1:1:size(EC,2)  
       match{k,1}=k;
      for s=1:1:size(D,2)
          if isequal(class(D{s}),class(EC{k}))  && isequal(EC{k},D{s})
              match{k}=[match{k} s];
          end
      end
  end
match{:}
ans =
     1
ans =
     2     1
ans =
     3
ans =
     4     2