%BETAPARMS—Compute parameters for a beta distribution

[TomDoan]

This function returns a 2-vector with the parameters for a beta distribution which has a requested mean and standard deviation. The beta is often used for the prior for a model parameter which has support on (0,1) and can be adapted easily to handle support on more general finite intervals.

betaparms.src

Function file

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Because it's a function (not a procedure), you need to do a SOURCE instruction on the file before you can use it in a RATS program.

target VECTOR=%BetaParms(mean,sd)

The mean must in the range (0,1) and the standard deviation in (0,sqrt(mean*(1-mean)))

Example
source betaparms.src (needs to be done once)
compute bparms=%BetaParms(.50,.20)
set test 1 1000 = %ranbeta(bparms(1),bparms(2))
set logg 1 1000 = %logbetadensity(test,bparms(1),bparms(2))

will create a series named TEST with beta draws with (population) mean .5 and standard deviation .2 and the log density (in LOGG) at each drawn value.

[jonasdovern]

Dear RATS users,

is there any simple way to obtain the CDF of a "generalized" beta distribution with support over a to b (rather than 0 to 1) using the basic functions available in RATS?

(I'd like to estimate the parameters of such a distribution based on empirically observed CDF-values from surveys (I have probabilities assigned to different "bins"/forecast intervals) using NLLS.)

Best regards,
Jonas

[TomDoan]

Dear RATS users,

is there any simple way to obtain the CDF of a "generalized" beta distribution with support over a to b (rather than 0 to 1) using the basic functions available in RATS?

(I'd like to estimate the parameters of such a distribution based on empirically observed CDF-values from surveys (I have probabilities assigned to different "bins"/forecast intervals) using NLLS.)

Best regards,
Jonas

With support on [a,b] and shape parameters alpha,beta:

compute cdfgbeta=%betainc((x-a)/(b-a),alpha,beta)