I need help with "apply". Below, I have no problem getting the column sums. 1. How do I get the sum of squares? 2. In general, where do I look up these functions? Thanks. x<-matrix(1:10,nrow=5); x sum <- apply(x,2,sum); sum [[alternative HTML version deleted]]
> s2 <- apply(x*x, 2, sum) > s2[1] 55 330 Jim Holtman Data Munger Guru What is the problem that you are trying to solve? Tell me what you want to do, not how you want to do it. On Tue, Oct 30, 2018 at 10:28 PM Steven Yen <styen at ntu.edu.tw> wrote:> > I need help with "apply". Below, I have no problem getting the column sums. > 1. How do I get the sum of squares? > 2. In general, where do I look up these functions? > Thanks. > > x<-matrix(1:10,nrow=5); x > sum <- apply(x,2,sum); sum > > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.
It should be said that for many basic statistics, there are faster
functions than apply, for example here you want
sum = colSums(x)
As already said, for sum of squares you would do colSums(x^2).
Many useful functions of this kind are implemented in package
matrixStats. Once you install it, either look at the package manual or
type ls("package:matrixStats") to see a list of functions. Most if not
all have self-explanatory names.
HTH,
Peter
On Tue, Oct 30, 2018 at 7:28 PM Steven Yen <styen at ntu.edu.tw>
wrote:>
> I need help with "apply". Below, I have no problem getting the
column sums.
> 1. How do I get the sum of squares?
> 2. In general, where do I look up these functions?
> Thanks.
>
> x<-matrix(1:10,nrow=5); x
> sum <- apply(x,2,sum); sum
>
>
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
Indeed. But perhaps it's also worth noting that if such statistics are calculated as implementations of (e.g. anova) formulae still found (sadly) in many statistics texts, then they shouldn't be calculated at all. Rather, the appropriate matrix methods (e.g. QR decompositions ) built into R -- many of which are already incorporated into R's statistical corpus -- should be used. To say more would of course be far O/T. Cheers, Bert Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) On Tue, Oct 30, 2018 at 8:44 PM Peter Langfelder <peter.langfelder at gmail.com> wrote:> It should be said that for many basic statistics, there are faster > functions than apply, for example here you want > > sum = colSums(x) > > As already said, for sum of squares you would do colSums(x^2). > > Many useful functions of this kind are implemented in package > matrixStats. Once you install it, either look at the package manual or > type ls("package:matrixStats") to see a list of functions. Most if not > all have self-explanatory names. > > HTH, > > Peter > On Tue, Oct 30, 2018 at 7:28 PM Steven Yen <styen at ntu.edu.tw> wrote: > > > > I need help with "apply". Below, I have no problem getting the column > sums. > > 1. How do I get the sum of squares? > > 2. In general, where do I look up these functions? > > Thanks. > > > > x<-matrix(1:10,nrow=5); x > > sum <- apply(x,2,sum); sum > > > > > > > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >[[alternative HTML version deleted]]
On 10/31/18 3:47 PM, jim holtman wrote:>> s2 <- apply(x*x, 2, sum) >> s2 > [1] 55 330<SNIP> It seems to me to be more "natural" (and perhaps more amenable to generalisation) to do: s2 <- apply(x,2,function(v){sum(v^2)}) But it's probably just a matter of taste. cheers, Rolf -- Technical Editor ANZJS Department of Statistics University of Auckland Phone: +64-9-373-7599 ext. 88276