rafael.7 at poczta.fm
2013-Sep-28 15:18 UTC
[R] Strange result from single [] extract operator
Hi All, I am using Rx64 3.0.1 on Windows 7 x64, and wanted to get two last rows from dataset. First, I tried library(datasets)> data<-airquality > data[nrow(data)-1:nrow(data),]and received 152 rows sorted desc. Could you explain why it worked this way? I changed the extract line to: data[(nrow(data)-1):nrow(data),] and then I received what I wanted but still am curious about the performance of my previous code. Yours faithfully, Rafa?
> First, I tried > library(datasets) > > data<-airquality > > data[nrow(data)-1:nrow(data),] > > and received 152 rows sorted desc. Could you explain why it worked this way? I changed > the extract line to: > data[(nrow(data)-1):nrow(data),] > > and then I received what I wanted but still am curious about the performance of my > previous code.Back up a little and compare nrow(data)-1:nrow(data) to (nrow(data)-1):nrow(data) or compare 3-1:3 to (3-1):3 Then look at the help file for "Syntax". Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com> -----Original Message----- > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf > Of rafael.7 at poczta.fm > Sent: Saturday, September 28, 2013 8:18 AM > To: r-help at r-project.org > Subject: [R] Strange result from single [] extract operator > > Hi All, > > I am using Rx64 3.0.1 on Windows 7 x64, and wanted to get two last rows from dataset. > First, I tried > library(datasets) > > data<-airquality > > data[nrow(data)-1:nrow(data),] > > and received 152 rows sorted desc. Could you explain why it worked this way? I changed > the extract line to: > data[(nrow(data)-1):nrow(data),] > > and then I received what I wanted but still am curious about the performance of my > previous code. > > Yours faithfully, > Rafa? > > ______________________________________________ > R-help at r-project.org mailing list > 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.
See Circle 8.1.3 of 'The R Inferno'. http://www.burns-stat.com/documents/books/the-r-inferno/ Pat On 28/09/2013 16:18, rafael.7 at poczta.fm wrote:> Hi All, > > I am using Rx64 3.0.1 on Windows 7 x64, and wanted to get two last rows from dataset. First, I tried > library(datasets) >> data<-airquality >> data[nrow(data)-1:nrow(data),] > > and received 152 rows sorted desc. Could you explain why it worked this way? I changed the extract line to: > data[(nrow(data)-1):nrow(data),] > > and then I received what I wanted but still am curious about the performance of my previous code. > > Yours faithfully, > Rafa? > > ______________________________________________ > R-help at r-project.org mailing list > 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. >-- Patrick Burns pburns at pburns.seanet.com twitter: @burnsstat @portfolioprobe http://www.portfolioprobe.com/blog http://www.burns-stat.com (home of: 'Impatient R' 'The R Inferno' 'Tao Te Programming')