How to output a random element from a vector in matlab?

I want to create a function called choose, where for example i can put in the command window choose(1:10) and the output would be a random number from 1 to 10. How do I do that?

Answer 1

[Walter Roberson]

choose = @(samples) samples(randi(numel(samples)));

[per isakson]

That's clever!

[Torsten]

Say you have a vector x of n numbers :

x = (x(1),x(2),...,x(n))

Now choosing a random element from this vector means to choose a number between 1 and n randomly and then return the element of x corresponding to that number. E.g. if 5 is chosen, x(5) is returned.

MATLAB's function "randi" can be used for this purpose. The command

randi(n)

returns a random integer between 1 and n.

So if you have a vector x, you can choose a random element from this vector by doing

n = numel(x);        % determines the number of elements of vector x
i = randi(n);        % returns a random integer between 1 and n
xrand = x(i);        % xrand is the randomly chosen element from vector x

Answer 2

[per isakson]

One way

>> cssm(1:10)
ans =
     2
>> cssm([3,6,9,12,1,2])
ans =
     3
>> cssm(1:10)
ans =
     6
>> cssm([3,6,9,12,1,2])
ans =
     2

where

function   val = cssm( vec )
    ix  = randi([1,length(vec)]);
    val = vec(ix);
end

[Hussam Alzahrani]

Thanks! it worked. could you explain how the function works?

[per isakson]

• see: &nbsp randi, Uniformly distributed pseudorandom integers
• see: &nbsp Examine Values While Debugging
• set a break point at the first line of the function
• call the function
• etc.

[Lawrence Prophete]

ix randomixes the index from 1 to the length of the vector, then val is the value of the randomized index