[R] Too slow to execute!
rolf at math.unb.ca
rolf at math.unb.ca
Sun Apr 29 18:44:16 CEST 2007
Chuck Cleland wrote:
<snip>
> Why use a loop here at all? It seems like this would do it pretty fast:
>
> Re <- rnorm(n = 2e+06, mean = - 1)
>
> > system.time(Re <- rnorm(n = 2e+06, mean = - 1))
> [1] 0.77 0.01 0.78 NA NA
>
> I'm not sure what you expect Re to be (a list with 100000 vectors of
> length 20?), but you could reshape one long vector into a matrix or
> whatever you might need. For example:
>
> Re.mat <- matrix(Re, ncol=20)
<snip>
Ummmmmm, not that it really matters, but doesn't the
original construction (x-2*10)/20, give variates with
mean = -1 and standard deviation = 1/20 = 0.05?
(One wonders why ``(x-2*10)/20'' rather than ``(x-20)/20'',
even if one allows for doing the operation in this
convoluted way.)
It might be added that ``Re'' is not a good name for
an object since it is the name of a function (which
returns the real part of complex numbers).
cheers,
Rolf Turner
rolf at math.unb.ca
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