Quantile function - different values in different versions of Matlab

Hello!

I have a complicated code, which worked perfectly in Matlab R2011b, but gives me wrong numbers in Matlab R2012b. I found out that the reason is that the quantile function gives different outputs in these two different versions of Matlab. I will not show you my code, since it is long and the problem can be illustrated by the following very simple example:

a=[1:98];
quantile(a,0.05)'

Output, Matlab R2011b: 5

Output, Matlab R2012b: 5.40

My problem is that I would like to use the newer version (R2012b) and get the result 5. The reason is that in the later step, I will have to use the find function:

index=find(a==quantile(a,0.05))

which obviously gives me an empty matrix, because the number 5.40 is not there. However, in the old version (R2011b), it would give an index, because number 5 is in the vector.

So, the question is: "How can I get the new version of Matlab to pick the element FROM the vector that is closest to the 5% quantile"

Thank you very much for your time and consideration!

Answer 1

[Wayne King]

I get the answer 5.4 in both R2011b and in R2012b. I'm not sure why you are getting 5 in R2011b. Perhaps you are using a non-MathWorks' version of quantile in R2011b?

If you enter

 >> which quantile

do you get some path back like:

matlab\toolbox\stats\stats\quantile.m

In your case you can always use:

a=[1:98];
round(quantile(a,0.05))

[Youssef Khmou]

right, its 5.400 even in older version .

Answer 2

[Youssef Khmou]

hi, You can resolve this problem by simply opening the function "quantile" in Mat2011b copy it and past it in your directory "Root_Mat\toolbox\stats\quantile011.m" name it "quantile011.m" to keep both versions .

Answer 3

[Aleksandrs]

Thank you very much!

I have tried

which quantile

on the machine with the old version. It turned out that there was another quantile function, which matlab was using. Thank you very much, everybody!