Compare two numeric cell arrays

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Russell Marki 2017-1-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/320676-compare-two-numeric-cell-arrays

评论： Russell Marki 2017-1-17

I have two huge cells, a dictionary and a set of possible hands in scrabble. I want to compare the two and find what arrays match

myAletters = ['D','I','R','N','E','E','P'];
myAletters = upper(myAletters);
myAletters = int8(myAletters);
myAletters = myAletters-64;
hand_count=0;
for i=1:length(myAletters)
      hand_interim_combination=nchoosek(myAletters,i);
      for j=1:length(hand_interim_combination(:,1))
          hand_interim_permutation=perms(hand_interim_combination(j,:));
           for k=1:length(hand_interim_permutation(:,1))
               hand_count=hand_count+1;
               hand{hand_count}=hand_interim_permutation(k,:);
           end
      end
end
end
load('myDict.mat');
word_plays=ismember(hand,myDict);

Ismember won't work because it has to be strings, going one by one won't work because it takes too long. Wat do?

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Andrei Bobrov 2017-1-17

Please attach your file myDict.mat.

Stephen23 2017-1-17

编辑：Stephen23 2017-1-17

在 MATLAB Online 中打开

"going one by one won't work because it takes too long. Wat do?"

Stop ignoring mlint messages in the Editor. There is already one message in your code telling you that the way you have written it is going to be slow. The message even tells you how to solve this issue:

Also note that the following code does not create an array of separate characters, because [] is a concatenation operator, not a list operators as many beginners think:

 >> myAletters = ['D','I','R','N','E','E','P']
 myAletters =
 DIRNEEP

That code is therefore equivalent to simply writing this:

 >> myAletters = 'DIRNEEP'
 myAletters =
 DIRNEEP

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Answer 1

Stephen23 2017-1-17

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https://ww2.mathworks.cn/matlabcentral/answers/320676-compare-two-numeric-cell-arrays#answer_250855

编辑：Stephen23 2017-1-17

在 MATLAB Online 中打开

Once I got rid of that unnecessary conversion to numeric value then this task becomes a lot easier. I also preallocated the cell array hand to significantly speed the code up.

myAletters = 'DIRNEEP';
hand = cell(1,floor(exp(1)*factorial(numel(myAletters)))-1);
hand_count=0;
for i=1:length(myAletters)
      hand_interim_combination=nchoosek(myAletters,i);
      for j=1:length(hand_interim_combination(:,1))
          hand_interim_permutation=perms(hand_interim_combination(j,:));
           for k=1:length(hand_interim_permutation(:,1))
               hand_count=hand_count+1;
               hand{hand_count}=hand_interim_permutation(k,:);
           end
      end
end
%load('myDict.mat');
myDict = {'IRE','PEER','XYZ'};
word_plays = ismember(hand,myDict);

and checking the output:

>> hand(word_plays) 
ans = 
  'IRE'    'IRE'    'PEER'    'PEER'

I also tidied up the formatting (crtl+I), replaced unpredictable length with reliable size, and renamed variables to make it more readable (for me):

vec = 'DIRNEEP';
hand = cell(1,floor(exp(1)*factorial(numel(vec)))-1);
itr = 0;
for m = 1:numel(vec)
    cmb = nchoosek(vec,m);
    for n = 1:size(cmb,1)
        prm = perms(cmb(n,:));
        for k = 1:size(prm,1)
            itr = itr+1;
            hand{itr} = prm(k,:);
        end
    end
end

Perhaps the simplest solution would be to use cellstr instead of the innermost loop:

vec = 'DIRNEEP';
hand = cell(1,2^numel(vec)-1);
k = 0;
for m = 1:numel(vec)
    cmb = nchoosek(vec,m);
    for n = 1:size(cmb,1)
        k = k+1;
        hand{k} = cellstr(perms(cmb(n,:)));
    end
end
hand = vertcat(hand{:});

Note that these are all just improvements on your algorithm. With a large dictionary a more efficient algorithm might use the small number of available letters to iteratively select smaller sets of the dictionary, until matches are achieved.