Error using the randi function

Here is my code:

function EPS

Score=zeros(1,20);

X=[0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1];
for j=1:20
Dealer=X(randi(numel(X)));
if sum(X)-.5*length(X)==0
Pick=X(randi(numel(X)));
else
    if sum(X)>size(X)
        Pick=1;
    if sum(X)<size(X)
        Pick=0;
    end
    end
end
if Pick==Dealer
    Score(j)=1;
end
X=X(X~=Dealer);
end
disp(sum(Score)/20);
end

When I run this I get an error on line 11 (Dealer variable as the for loop is line 10): Error using randi First input must be a positive scalar integer value IMAX, or two integer values [IMIN IMAX] with IMIN less than or equal to IMAX.

If I define X as I did in my code and in my command window type X(randi(numel(X))) I do not get an error.

Why is my code giving me the error if in the command window it is working?

[KSSV]

This line:

   X=X(X~=Dealer);

gives a empty matrix after few loops....so randi(emptymatrix) popping error.

[Walter Roberson]

Right. You have multiple equal values so X(X~=Dealer) is deleting multiple entries, all of the duplicates of Dealer. You only have two unique values in X, so after the second time you execute the line you would have deleted everything out of X.

Perhaps you should instead keep track of the random index and delete only that one item.

[Tony]

Thank you guys for your help!

Answer 1

[KSSV]

Score=zeros(1,20);
X=[0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1];
for j=1:20
    idx = randi(numel(X)) ;
    Dealer=X(idx);
    if sum(X)-.5*length(X)==0
        Pick=X(randi(numel(X)));
    else
        if sum(X)>size(X)
            Pick=1;
            if sum(X)<size(X)
                Pick=0;
            end
        end
    end
    if Pick==Dealer
        Score(j)=1;
    end
    X(idx) = [] ;
end
disp(sum(Score)/20);

[Tony]

Thanks!

[Jan]

if sum(X)<size(X) is tricky: Note that size replies a vector.