[R] deriv, loop

[francogrex]

Hi, 2 questions:

Question 1: example of what I currently do:

for(i in 1:6){sink("temp.txt",append=TRUE)
dput(i+0)
sink()}
x=scan(file="temp.txt")
print(prod(x))
file.remove("C:/R-2.5.0/temp.txt")

But how to convert the output of the loop to a vector that I can manipulate
(by prod or sum etc), without having to write and append to a file?

Question 2:

> deriv(~gamma(x),"x")

expression({
    .expr1 <- gamma(x)
    .value <- .expr1
    .grad <- array(0, c(length(.value), 1), list(NULL, c("x")))
    .grad[, "x"] <- .expr1 * psigamma(x)
    attr(.value, "gradient") <- .grad
    .value
})

BUT

> deriv3(~gamma(x),"x")
Error in deriv3.formula(~gamma(x), "x") : Function 'psigamma' is not in the
derivatives table

What I want is the expression for the second derivative (which I believe is
trigamma(x), or psigamma(x,1)), how can I obtain that?

Thanks
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