> I have created two functions to compute geometric means. Method 1 can
> handle even number of negative values but not large number, vice versa
> for method 2. How can I merge both functions so that both large number
> and negative values can be handled ?
>
> > geometric.mean1 <- function(x) prod(x)^(1/length(x))
> > geometric.mean2 <- function(x) exp(mean(log(x)))
>
> > geometric.mean1(1:10000000)
> [1] Inf
> > geometric.mean2(1:10000000)
> [1] 3678798
>
> > geometric.mean1(c(-5,-4,4,5))
> [1] 4.472136
> > geometric.mean2(c(-5,-4,4,5))
> [1] NaN
> Warning message:
> In log(x) : NaNs produced
Geometric mean is usually restricted to positive inputs, because otherwise
the answer can have an imaginary component. If you really want the
geometric mean of negative inputs, use the second method but convert the
input to be a complex number first.
comp.x <- as.complex(c(-5,-4,4,5))
geometric.mean2(comp.x)
# [1] 0+4.472136i
Regards,
Richie.
Mathematical Sciences Unit
HSL
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