[SciPy-User] specifying range in scipy.stats.truncnorm

Joon Ro joonpyro@gmail....
Fri Jul 27 11:30:29 CDT 2012


Hi,

I tried to use scipy.stats.truncnorm and found the way to specifying the 
parameters of truncated normal very confusing.
I expected a, b parameter to be the specification of the interval where 
I want to truncate the distribution at, but it is not the case when the 
normal I want to use is not standard.

According to the documentation, I need to standardize my values - for 
example, if I want to have a truncated normal with mean 0.5, variance 1, 
on [0, 1] interval, I need to do:

    myclip_a = 0
    myclip_b = 1
    my_mean=0.5
    my_std =1

    a, b = (myclip_a - my_mean) / my_std, (myclip_b - my_mean) / my_std

    rv = truncnorm(a, b, loc=my_mean, scale=my_std)

Which is unnecessarily complicated in my opinion. Since we have to 
provide location and scale parameter anyway, why not make truncnorm to 
accept the actual interval values (in this case, a, b = 0, 1) instead 
and do the standardization internally? I think it would be more 
intuitive that way.

Best regards,
Joon
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.scipy.org/pipermail/scipy-user/attachments/20120727/653e58fe/attachment.html 


More information about the SciPy-User mailing list