Indeed, it seems that the author of zipfR has neither been aware
that the (scaled / aka regularized) incomplete gamma (and beta,
for that matter!) functions have been part of R all along.
...
... well , inspecting his code reveals he did know it.
But why then on earth provide all the n
RV> I would be very grateful if you could help me with:
RV> Given the regularized gamma function Reg=int_0^r
RV> (x^(k-1)e^(-x))dx/int_0^Inf (x^(k-1)e^(-x))dx ; 0 (which is eventually the ratio of the Incomplete gamma
RV> function by the gamma function),
and which is exactly what
You can do this using the package "numDeriv".
require(zipfR)
require(numDeriv)
fn <- function(x, y) Rgamma.inv(x, y)
gRgamma.inv <- function(y, k) sapply(y, function(y) grad(x=k, func=fn, y=y))
plot(gRgamma.inv(y=seq(0,1, length=200), k=1), type="l", xlab="x",
ylab="Derivative of Rgamma.inv w
I would be very grateful if you could help me with:
Given the regularized gamma function Reg=int_0^r (x^(k-1)e^(-x))dx/
int_0^Inf (x^(k-1)e^(-x))dx ; 0of the
Incomplete gamma function by the gamma function), does anyone know
of a package in R that would evaluate the derivative of the inverse
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