On 2011-07-25 12:24, Sam Albers wrote:
Hello R-help,I have some data collected at regular intervals but for a varying length of time. I would like to standardize the length of time collected and I can do this by standardizing the number of records I use for my analysis. Take for example the data set below: library(plyr) x<- runif(18,10, 15) df<- as.data.frame(x) df$fac<- factor(c("Test1","Test1","Test1","Test1","Test1","Test1","Test1", "Test2","Test2","Test2","Test2","Test2", "Test3","Test3","Test3","Test3","Test3","Test3")) ## Here is where I would like to standardize the number of records df.avg<- ddply(df, c("fac"), function(df) return(c(x.avg=mean(df$x), n=length(df$x)))) df.avg Here there is a different number of records for each factor level. Say I only wanted to use the first 4 records at each factor level. Prior to taking the mean of these values how might I drop all the records after 4? Can anyone suggest a good way to do this?
Just subset in your function definition: mean(df$x) --> mean(df$x[1:4]) But I would use summarize: ddply(df, .(fac), summarize, x.avg = mean(x[1:4]), n = length(x)) Peter Ehlers
I am using R 2.12.1 and Emacs + ESS. Thanks so much in advance. Sam ______________________________________________ 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.
