Nice. I was thinking maybe length(table(x) == 1), but this works great > -----Original Message----- > From: Carlos J. Gil Bellosta [mailto:c...@datanalytics.com] > Sent: Tuesday, January 13, 2009 2:55 PM > To: Doran, Harold > Cc: r-help@r-project.org > Subject: Re: [R] Comparing elements for equality > > Hello, > > You could build your output dataframe along the following lines: > > foo <- function(x) length( unique(x) ) == 1 > > results <- data.frame( > freq = tapply( dat$id, dat$id, length ), > var1 = tapply( dat$var1, dat$id, foo ), > var2 = tapply( dat$var2, dat$id, foo ) > ) > > Best regards, > > Carlos J. Gil Bellosta > http://www.datanalytics.com > > > On Tue, 2009-01-13 at 14:17 -0500, Doran, Harold wrote: > > Suppose I have a dataframe as follows: > > > > dat <- data.frame(id = c(1,1,2,2,2), var1 = > c(10,10,20,20,25), var2 = > > c('foo', 'foo', 'foo', 'foobar', 'foo')) > > > > Now, if I were to subset by id, such as: > > > > > subset(dat, id==1) > > id var1 var2 > > 1 1 10 foo > > 2 1 10 foo > > > > I can see that the elements in var1 are exactly the same and the > > elements in var2 are exactly the same. However, > > > > > subset(dat, id==2) > > id var1 var2 > > 3 2 20 foo > > 4 2 20 foobar > > 5 2 25 foo > > > > Shows the elements are not the same for either variable in this > > instance. So, what I am looking to create is a data frame > that would > > be like this > > > > id freq var1 var2 > > 1 2 TRUE TRUE > > 2 3 FALSE FALSE > > > > Where freq is the number of times the ID is repeated in the > dataframe. > > A TRUE appears in the cell if all elements in the column > are the same > > for the ID and FALSE otherwise. It is insignificant which values > > differ for my problem. > > > > The way I am thinking about tackling this is to loop through the ID > > variable and compare the values in the various columns of > the dataframe. > > The problem I am encountering is that I don't think all.equal or > > identical are the right functions in this case. > > > > So, say I was wanting to compare the elements of var1 for id ==1. I > > would have > > > > x <- c(10,10) > > > > Of course, the following works > > > > > all.equal(x[1], x[2]) > > [1] TRUE > > > > As would a similar call to identical. However, what if I > only have a > > vector of values (or if the column consists of names) that > I want to > > assess for equality when I am trying to automate a process over > > thousands of cases? As in the example above, the vector may contain > > only two values or it may contain many more. The number of > values in > > the vector differ by id. > > > > Any thoughts? > > > > Harold > > > > ______________________________________________ > > R-help@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. > >
______________________________________________ R-help@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.
