How to remove elements from a matrix?

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?

[Adam]

doc randperm

[Stephen23]

Note that [] is a concatenation operator, so this

[ 't' 'h' 'e' 's' 't' 'r' 'i' 'n' 'g']

is simply identical to this:

'thestring'

Answer 1

[the cyclist]

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.

[John Mat]

Thanks u very much for the answer, how can i do the exact same thing without 'numberToKeep'? For instance, delete random elements without limit in numberToKeep.

[Adam]

U = [];

would be the quickest way!

[the cyclist]

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]

Thank u very much, u helped me a lot!

Answer 2

[Stephen23]

Use randperm (it has no repeats):

nkeep = 4;
str = 'thestring';
str(randperm(numel(str),nkeep))

[John Mat]

Sorry for my silly questions but im new at Matlab. I tried this code but i cant find the solution of my error.

str = 'thestring';
nkeep = randperm(length(str));
str = str(randperm(numel(str),nkeep));
disp(str)

I want nkeep to have random number from the length of the string. For example if the length of str is 13 then nkeep will be randomly 8.

[Stephen23]

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]

Thank you very much for the answers. You helped me a lot! :)