[R] Alternative to apply in base R

[Jeff Newmiller]

Log-sum-antilog is faster than apply by several times, but vector multiplication in a for loop as David and Chuck have suggested is several times faster than that. 
-- 
Sent from my phone. Please excuse my brevity.

On November 8, 2016 12:23:04 PM PST, "Doran, Harold" <HDoran at air.org> wrote:
>It¹s a good suggestion. Multiplication in this case is over 7 columns
>in
>the data, but the number of rows is millions. Unfortunately, the values
>are negative as these are actually gauss-quad nodes used to evaluate a
>multidimensional integral.
>
>colSums is better than something like apply(dat, 2, sum); I was hoping
>there was something similar to colSums/rowSums using prod().
>
>On 11/8/16, 3:00 PM, "Fox, John" <jfox at mcmaster.ca> wrote:
>
>>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-bounces at r-project.org] on behalf of Doran, Harold
>>[HDoran at air.org]
>>Sent: November 8, 2016 10:57 AM
>>To: r-help at 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)
>>
>>        [[alternative HTML version deleted]]
>>
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>
>______________________________________________
>R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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>and provide commented, minimal, self-contained, reproducible code.