How can I solve randperm error with words?

Question

Martha Spadaccino 2019-5-24

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/463845-how-can-i-solve-randperm-error-with-words

编辑： madhan ravi 2019-5-24

采纳的回答： madhan ravi

I had create this code

Tile = {'house', 'core', 'word', 'ask', 'question', 'horse', 'phone', 'eyes', 'hair', 'man'};

>> X = X(randperm(size(X,1)),:);

>> Error undefined function or variable X

I would have all possible random combinations pairs without repetitions and without have the same values (e.g horse - horse). How can I do?

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Stephen23 2019-5-24

编辑：Stephen23 2019-5-24

在 MATLAB Online 中打开

"I want a random order.."

What do you think this line of my answer is for?:

X = X(randperm(size(X,1)),:); % random row order.

Based on your question above, you are not runinng the complete code that i gave you. Exactly as Rik wrote, for some unknown reason you have decided to remove one lines of the code that I gave you. Of course it will not work if you remove a line of code!

This is the code I gave you, it does exactly as you requested (very efficiently!):

>> Tile = {'house', 'core', 'word', 'ask', 'question', 'horse', 'phone', 'eyes', 'hair', 'man'};
>> X = nchoosek(1:numel(Tile),2); % Why did you remove this?
>> X = X(randperm(size(X,1)),:);
>> Tile(X)

Martha Spadaccino 2019-5-24

Thank you so much! I definitively resolved the problem.

>> Tile = {'house', 'core', 'word', 'ask', 'question', 'horse', 'phone', 'eyes', 'hair', 'man'};

>> X = nchoosek(1:numel(Tile),2); % Why did you remove this? I thought to remove it..sorry!

>> X = X(randperm(size(X,1)),:);

>> Tile(X)

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Answer 1

madhan ravi 2019-5-24

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https://ww2.mathworks.cn/matlabcentral/answers/463845-how-can-i-solve-randperm-error-with-words#answer_376480

编辑：madhan ravi 2019-5-24

在 MATLAB Online 中打开

[x,y]=ndgrid(Tile);
xy=[x(:),y(:)];
xy(~strcmp(xy(:,1),xy(:,2)),:)

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Stephen23 2019-5-24

编辑：Stephen23 2019-5-24

Neat use of ndgrid directly on the cell array!

Something to keep in mind: this ndgrid-based method generates much larger intermediate arrays than the final array, because the intermediate arrays include duplicate sets and repeated strings, before they simply get discarded. For small sets of strings this might not be a problem (for larger sets the nchoosek-based method used in my answer will use less memory).

Note that this answer does not return the rows in a random order, which the question requires: you will need to add randperm or similar.

@madhan ravi: apparently this error is due to an undocumented change in ndgrid. See:

https://www.mathworks.com/matlabcentral/answers/392649-generate-combinations-of-cells-that-contain-text#comment_707380

Does the installed ndgrid help mention anything about supporting strings or cell arrays ?

madhan ravi 2019-5-24

编辑：madhan ravi 2019-5-24

在 MATLAB Online 中打开

Thanks you Stephen, I definitely would have not answered if this question was already asked (as it seem to be). I am not going to remove the answer as Stephen’s comment is really valuable. This answer doesn’t meet the requirements as it was given as I was walking and gave the answer using my mobile which didn’t require enough brain efficiency.

Perhaps:

[x,y]=ndgrid(Tile);
xy=[x(:),y(:)];
filteredxy = xy(~strcmp(xy(:,1),xy(:,2)));
xy(randperm(size(filteredxy,1)),:) % random order

No Stephan help ndgrid doesn't mention anything about that.

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Answer 2

KSSV 2019-5-24

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https://ww2.mathworks.cn/matlabcentral/answers/463845-how-can-i-solve-randperm-error-with-words#answer_376479

编辑：KSSV 2019-5-24

在 MATLAB Online 中打开

Tile = {'house', 'core', 'word', 'ask', 'question', 'horse', 'phone', 'eyes', 'hair', 'man'};
 % Gives random arrangement 
X = Tile(randperm(length(Tile))); 
  % get all posibilities 
idx = perms(1:length(Tile)) ;
iwant = Tile(idx) ;