How to remove elements from a matrix?

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John Mat
John Mat 2017-6-6
评论： John Mat 2017-6-6
I would like to delete random elements from this matrix: U = [ 't' 'h' 'e' 's' 't' 'r' 'i' 'n' 'g']
How can i do it?
  2 个评论
Stephen23
Stephen23 2017-6-6
Note that [] is a concatenation operator, so this
[ 't' 'h' 'e' 's' 't' 'r' 'i' 'n' 'g']
is simply identical to this:
'thestring'

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采纳的回答

the cyclist
the cyclist 2017-6-6
编辑：the cyclist 2017-6-6
If you have the Statistics and Machine Learning Toolbox, you can do
numberToKeep = 4;
U = U(sort(randsample(length(U),numberToKeep)));
If you do not have that toolbox, you can accomplish the same thing using a different random function, like randi, but you'll need to guard against repeated elements. Let us know if you get stuck.
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the cyclist
the cyclist 2017-6-6
John, are you saying that you don't even want to specify the number of elements to be removed at random ahead of time? You want that to be random, also?
If that is the case, then you can just define
numberToKeep = randi(length(U))
John Mat
John Mat 2017-6-6
Thank u very much, u helped me a lot!

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更多回答（1 个）

Stephen23
Stephen23 2017-6-6
编辑：Stephen23 2017-6-6
Use randperm (it has no repeats):
nkeep = 4;
str = 'thestring';
str(randperm(numel(str),nkeep))
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Stephen23
Stephen23 2017-6-6
编辑：Stephen23 2017-6-6
If you want to keep the same order, and have random number of characters removed, then you could do this:
>> str = 'thestring';
>> N = numel(str);
>> str(randperm(N,randperm(N,1))) = []
str = teting
or use randi instead:
>> str = 'thestring';
>> N = numel(str);
>> str(randperm(N,randi(N,1))) = []
str = ttrin
John Mat
John Mat 2017-6-6
Thank you very much for the answers. You helped me a lot! :)

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