Hello all,
I am trying to get a better understanding of the underlying code for the
stats::dpois function in R and, specifically, what happens under the hood when
it is called. I finally managed to track down the C course at:
https://github.com/wch/r-source/blob/trunk/src/nmath/dpois.c. It would seem
that the dpois C function is taking a double for each of the x and lambda
arguments so I am a bit confused why I can provide a vector and matrix to dpois
in R, e.g.
dpois(1:5, matrix(runif(2*5, 1, 10), nrow = 5)))
and get a matrix back with the results. Due to this, I was expecting to see a
loop, or similar, in the underlying C source but… to no avail. So I have to
conclude that either a) there is a step between when I call dpois in R and the
C code getting executed that loops over the inputs or b) that there is a
construct in the C code (my proficiency here is limited) that is called per
input. Any help in enlightening me on what code is responsible for iterating
over the multiple inputs (or if someone is feeling energetic, the exact
stepwise code that is executed when calling dpois) would be greatly
appreciated!!
Kind Regards,
Jason Serviss
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