[R] Using nrow with summaryBy
Hello Everyone- I'm calculating summary statistics on a dataset (~4000 records, observations are not uniformly distributed) using summaryBy and trying to add a column with the number of observations to the output as well. What occurs to me is to use nrow(), but this doesn't appear to be working I'm able to replicate the same results with an example from the summaryBy docs: data(dietox) dietox12- subset(dietox,Time==12) library(doBy) #this one works summaryBy(Weight+Feed~Evit+Cu,data=dietox12,FUN=c(mean,var,length)) #adding nrow doesn't give the number of rows summaryBy(Weight+Feed~Evit+Cu,data=dietox12,FUN=c(mean,var,length,nrow)) There must be a way to do this, but I can't figure it out. I suspect there is another function that would be compatible with summaryBy. Thanks in advance. -Tony [[alternative HTML version deleted]] __ 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.
Re: [R] Using nrow with summaryBy
On Mar 17, 2010, at 11:23 AM, Tony Laidig wrote: Hello Everyone- I'm calculating summary statistics on a dataset (~4000 records, observations are not uniformly distributed) using summaryBy and trying to add a column with the number of observations to the output as well. What occurs to me is to use nrow(), but this doesn't appear to be working I'm able to replicate the same results with an example from the summaryBy docs: data(dietox) dietox12- subset(dietox,Time==12) library(doBy) #this one works summaryBy(Weight+Feed~Evit+Cu,data=dietox12,FUN=c(mean,var,length)) #adding nrow doesn't give the number of rows summaryBy(Weight+Feed~Evit +Cu,data=dietox12,FUN=c(mean,var,length,nrow)) I'm a bit puzzled. One of my many newbie mistakes was to assume that length() applied to dataframes would tell me how many rows it had. It appears that the authors of summaryBy have figured out how to get length() to tell you the number of observations, presumably on a subsetted vector where length would make sense. So ... it's not clear why you also want nrow (which would not make sense for a subsetted vector). There must be a way to do this, but I can't figure it out. I suspect there is another function that would be compatible with summaryBy. Thanks in advance. -Tony David Winsemius, MD West Hartford, CT __ 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.
Re: [R] Using nrow with summaryBy
Hi David, I have probably 2 stupid questions regarding what you said but it might be important to understand: - why nrow() would not make sens for a subsetted vector? On the help page of nrow(), it's written that we can apply it on a vector, array or dataframe (basically everything...?). So what's the difference between a normal vector (for which it would make sense and work) and a subsetted vector? - why assuming that length() applied to dataframes would tell me how many rows it had would be a mistake? I mean in this case, length() is calculated for each numerical variable (which are vectors, aren't they?). I think these questions concern the way R handle the data and that's why I think it might be important for me to understand these issues. Thanks for your input. Regards, Ivan Le 3/17/2010 16:39, David Winsemius a écrit : On Mar 17, 2010, at 11:23 AM, Tony Laidig wrote: Hello Everyone- I'm calculating summary statistics on a dataset (~4000 records, observations are not uniformly distributed) using summaryBy and trying to add a column with the number of observations to the output as well. What occurs to me is to use nrow(), but this doesn't appear to be working I'm able to replicate the same results with an example from the summaryBy docs: data(dietox) dietox12- subset(dietox,Time==12) library(doBy) #this one works summaryBy(Weight+Feed~Evit+Cu,data=dietox12,FUN=c(mean,var,length)) #adding nrow doesn't give the number of rows summaryBy(Weight+Feed~Evit+Cu,data=dietox12,FUN=c(mean,var,length,nrow)) I'm a bit puzzled. One of my many newbie mistakes was to assume that length() applied to dataframes would tell me how many rows it had. It appears that the authors of summaryBy have figured out how to get length() to tell you the number of observations, presumably on a subsetted vector where length would make sense. So ... it's not clear why you also want nrow (which would not make sense for a subsetted vector). There must be a way to do this, but I can't figure it out. I suspect there is another function that would be compatible with summaryBy. Thanks in advance. -Tony David Winsemius, MD West Hartford, CT __ 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. -- Ivan CALANDRA PhD Student University of Hamburg Biozentrum Grindel und Zoologisches Museum Abt. Säugetiere Martin-Luther-King-Platz 3 D-20146 Hamburg, GERMANY +49(0)40 42838 6231 ivan.calan...@uni-hamburg.de ** http://www.for771.uni-bonn.de http://webapp5.rrz.uni-hamburg.de/mammals/eng/mitarbeiter.php __ 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.
Re: [R] Using nrow with summaryBy
On Mar 17, 2010, at 12:10 PM, Ivan Calandra wrote: Hi David, I have probably 2 stupid questions regarding what you said but it might be important to understand: - why nrow() would not make sens for a subsetted vector? On the help page of nrow(), it's written that we can apply it on a vector, array or dataframe (basically everything...?). So what's the difference between a normal vector (for which it would make sense and work) and a subsetted vector? nrow(c(0,1,3,4)) NULL nrow(1:12) NULL (It did not throw an error but the help page does say the value could be NULL.) length(1:12) [1] 12 - why assuming that length() applied to dataframes would tell me how many rows it had would be a mistake? I mean in this case, length() is calculated for each numerical variable (which are vectors, aren't they?). length applied to any list is the number of elements at the first level. Dataframes are lists of vectors so length applied to data.frames gives you the number of columns, not the length of an individual vector in the dataframe. I think these questions concern the way R handle the data and that's why I think it might be important for me to understand these issues. It's important, fur sure. Thanks for your input. Regards, Ivan Le 3/17/2010 16:39, David Winsemius a écrit : On Mar 17, 2010, at 11:23 AM, Tony Laidig wrote: Hello Everyone- I'm calculating summary statistics on a dataset (~4000 records, observations are not uniformly distributed) using summaryBy and trying to add a column with the number of observations to the output as well. What occurs to me is to use nrow(), but this doesn't appear to be working I'm able to replicate the same results with an example from the summaryBy docs: data(dietox) dietox12- subset(dietox,Time==12) library(doBy) #this one works summaryBy(Weight+Feed~Evit+Cu,data=dietox12,FUN=c(mean,var,length)) #adding nrow doesn't give the number of rows summaryBy(Weight+Feed~Evit +Cu,data=dietox12,FUN=c(mean,var,length,nrow)) I'm a bit puzzled. One of my many newbie mistakes was to assume that length() applied to dataframes would tell me how many rows it had. It appears that the authors of summaryBy have figured out how to get length() to tell you the number of observations, presumably on a subsetted vector where length would make sense. So ... it's not clear why you also want nrow (which would not make sense for a subsetted vector). There must be a way to do this, but I can't figure it out. I suspect there is another function that would be compatible with summaryBy. Thanks in advance. -Tony David Winsemius, MD West Hartford, CT __ 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. -- Ivan CALANDRA PhD Student University of Hamburg Biozentrum Grindel und Zoologisches Museum Abt. Säugetiere Martin-Luther-King-Platz 3 D-20146 Hamburg, GERMANY +49(0)40 42838 6231 ivan.calan...@uni-hamburg.de ** http://www.for771.uni-bonn.de http://webapp5.rrz.uni-hamburg.de/mammals/eng/mitarbeiter.php __ 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. David Winsemius, MD West Hartford, CT __ 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.
Re: [R] Using nrow with summaryBy
Use NROW rather than nrow. On Wed, Mar 17, 2010 at 11:23 AM, Tony Laidig c...@mit.edu wrote: Hello Everyone- I'm calculating summary statistics on a dataset (~4000 records, observations are not uniformly distributed) using summaryBy and trying to add a column with the number of observations to the output as well. What occurs to me is to use nrow(), but this doesn't appear to be working I'm able to replicate the same results with an example from the summaryBy docs: data(dietox) dietox12- subset(dietox,Time==12) library(doBy) #this one works summaryBy(Weight+Feed~Evit+Cu,data=dietox12,FUN=c(mean,var,length)) #adding nrow doesn't give the number of rows summaryBy(Weight+Feed~Evit+Cu,data=dietox12,FUN=c(mean,var,length,nrow)) There must be a way to do this, but I can't figure it out. I suspect there is another function that would be compatible with summaryBy. Thanks in advance. -Tony [[alternative HTML version deleted]] __ 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.
