In R the cumulative distribution function for the binomial distribution is called via an underlying C/C++ function called C_pbinom. I am trying to find the underlying code for this algorithm, so that I can find out what algorithm this function uses to compute the cumulative distribution function. Unfortunately, I have not been successful in finding the underlying code, nor any information on the algorithm that is used.
My question: How do I find the underlying C/C++ code for the function C_pbinom. Alternatively, is there any information source available showing the algorithm used by this function?
What I have done so far: Calling pbinom in R gives the following details:
function (q, size, prob, lower.tail = TRUE, log.p = FALSE)
.Call(C_pbinom, q, size, prob, lower.tail, log.p)
<bytecode: 0x000000000948c5a0>
<environment: namespace:stats>
I have located and opened the underlying NAMESPACE file in the stats library. This file lists various functions, including the pbinom function, but does not give code for the C_pbinom function, nor any pointer to where it can be found. I have also read a related answer on finding source code in R, and an article here on "compiling source codes", but neither has been of sufficient assistance to let me find the code. At this point I have his a dead end.
