[Rcpp-devel] Using complex numbers and functions in Rcpp
Martin S Ridout
M.S.Ridout at kent.ac.uk
Tue Feb 21 16:46:35 CET 2017
Apologies if this is a naive question - I'm a beginner with Rcpp. I did see some earlier discussion on similar topic, but I don't think it answered my questions.
I am trying (on Windows) to speed up a function currently written in R. This works very well for real-valued arguments of the function. But it needs to work for complex arguments as well. Here is a stripped down (but still non-working) example of what I am trying to do
cppFunction('
ComplexVector test(ComplexVector s, ComplexVector lambda) {
int n = s.size();
int m = lambda.size();
ComplexVector out(n);
for (int i=0; i < n; ++i) {
for (int j=0; j < m; ++j) {
out[i] = out[i] - log(s[i] + 1/lambda[j]) / 2;
}
}
return out;
}
')
I have (at least) 2 problems
i) Are the logarithm and exponential functions implemented for complex arguments? If not is there a work-around?
ii) What is the best way to specify constants like 1 and 2 as complex constants? This must be easy, but everything I tried so far gives an error (except passing them into the function via an extra ComplexVector argument, but there must be a better way).
Many thanks for any help,
Martin Ridout
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