Hi all, I'm just getting started in R. My problem is the following:
I have a data frame (v1) with lots of production data measurements. Each row contains a single measurement ('ARI_MIT') with a timestamp. I want to "lump" the data by months with their mean and standard deviation. I have already successfully managed to do the lumping by adding another column to my data frame: v1$MONTH = strftime(v1$TIMESTAMP, "%y%m") This makes a nice month-wise boxplot of my data, although I don't have an idea why: boxplot(v1$ARI_MIT ~ v1$MONTH) I don't need this plotted, though, but in the form of a new data frame with three columns: the month, the mean, and the standard deviation of all values from that month. I tried un-stacking v1 into a list of vectors and then looping over its elements, calculating the mean of each group: for (i in unstack(v1, v1$ARI_MIT ~ v1$MONTH)) { write(mean(i), "") } This works, but how do I get the data into a data frame? With the month labels in a column? They are not avaliable inside the loop body. I know I need to get a book on R. Thanks, robert ______________________________________________ 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.