dgamma() function

[Brook Milligan]

Hi,

I am calling dgamma() withing a Nimble function like so:

lp <- dgamma(x, shape=shape, scale=scale, log)

but get the following error message:

Error in dgamma(x, shape = shape, scale = scale, log) : specify 'rate' or 'scale' but not both

As far as I can tell, I am in fact specifying scale, not rate. The synopsis for the R dgamma() function is:

dgamma(x, shape, rate = 1, scale = 1/rate, log = FALSE)

and the synopses for the Nimble dgamma() function are:

dgamma(shape, scale) canonical
dgamma(shape, rate) dgamma(shape, scale = 1 / rate)
dgamma(mean, sd) dgamma(shape = mean^2/sd^2, scale = sd^2/mean)

I’m not sure which gets called from within a Nimble function but I expect the scale/shape parameterization to work with either.

By the way, should there be a log parameter for the Nimble synopses, or do they never take that argument?

What am I missing here?

Thanks for your help.

Cheers,
Brook

[Benjamin R Goldstein]

Hi Brook—

Since it’s unnamed in your code, think “log” is getting input to the function as the next parameter (rate). Does it work if you do 

        lp <- dgamma(x, shape=shape, scale=scale, log=log)

?

Hope this helps,

Ben

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[Brook Milligan]

Yes, that works. Thanks for spotting this. Sometimes the obvious things are just in front of you.

Cheers,
Brook

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