Binornd draws '1' every time

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Henry on 8 Jul 2014
Commented: Henry on 8 Jul 2014
I'm running a script in which I use binornd(1,0.5) within a for loop, and the output is '1' every time. When I copy paste to the command window, it behaves as expected (I haven't done a full statistical test, but at least I get both '0's and '1's as outputs). In the same script, I use randi, which seems to be behaving normally..
Moving the binornd line to different positions in the script does not make a difference, and neither does adding rng('shuffle') just above. Finally, I use binornd(1,p) in another loop, where p varies on each iteration, and I also get only '1's as outputs. So it seems to be a problem specific to binornd.
Henry on 8 Jul 2014
Can't see why, but problem resolved after making some changes elsewhere in the code. Thanks everyone.

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Answers (2)

Jos (10584)
Jos (10584) on 8 Jul 2014
what if you execute
which binornd
just before the calls? Do the outputs differ based on the situation (script vs. command line). It could be that you have two different versions ...
  1 Comment
Henry on 8 Jul 2014
Thanks for the response. I tried this and I get the same version both times: C:\Program Files\MATLAB\R2014a\toolbox\stats\stats\binornd.m
But yes the outputs do differ between these 2 situations. I've now noticed that the 2nd time I call it, it is indeed working (just that the p values were high), but the first time is still failing (line 5 of the code I entered above). And changing p to any non-zero value below 1 does not change the situation.

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Shashank Prasanna
Shashank Prasanna on 8 Jul 2014
Edited: Shashank Prasanna on 8 Jul 2014
Why don't you generate all of your random numbers before hand and just use index into the array at each loop iteration? It should be faster and cleaner:
randBin = binornd(limit,0.5);
while count<limit
a(count)=randi([1 order]);
b(count)=randi([1 order]);
Henry on 8 Jul 2014
OK thanks. And the problem resolved itself a few minutes ago when I made some changes somewhere else in the code. It's still not at all clear to me why, but at least it's working!

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