Dear Harold,
If the actual data with which you're dealing are non-negative, you could log
all the values, and use colSums() on the logs. That might also have the
advantage of greater numerical accuracy than multiplying millions of numbers.
Depending on the numbers, the products may be too large or small to be
represented. Of course, logs won't work with your toy example, where rnorm()
will generate values that are both negative and positive.
I hope this helps,
John
-----------------------------
John Fox, Professor
McMaster University
Hamilton, Ontario
Canada L8S 4M4
web: socserv.mcmaster.ca/jfox
________________________________________
From: R-help [r-help-boun...@r-project.org] on behalf of Doran, Harold
[hdo...@air.org]
Sent: November 8, 2016 10:57 AM
To: r-help@r-project.org
Subject: [R] Alternative to apply in base R
Without reaching out to another package in R, I wonder what the best way is to
speed enhance the following toy example? Over the years I have become very
comfortable with the family of apply functions and generally not good at
finding an improvement for speed.
This toy example is small, but my real data has many millions of rows and the
same operations is repeated many times and so finding a less expensive
alternative would be helpful.
mm <- matrix(rnorm(100), ncol = 10)
rn <- apply(mm, 1, prod)
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