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Dear R users, imagine i have a dataframe and an indexing vector with the length of the amount of columns of the dataframe. Is there any convenient way to combine the colums of the dataframe into vectors (or straight away apply fundtions to these subsets) according to the indexing vector in a similar manner to the tapply function? For example, in the follwoing case, I would like to combine columns 1 and two into one vector, and columns 3-4 into another: test???? = as.data.frame(matrix(1:20, ncol = 5, nrow=4)) test.ind =c(1,1...

...tion. Easy one is to look at only rank1 column, then I do not utilize all information the data have. I can also do this. For each product, the number of people * rank scores and then pick lowest number for the best product. Is there any other way I can summarize this data? Any suggestion for R fundtions or statistical methos will be appreciated. Taka, _________________________________________________________________ Get today's hot entertainment gossip http://movies.msn.com/movies/hotgossip

Hi. I am starting to learn R for a course project. I am relative OK c++ programer. I found the R is very different. I have read the "an introduction to R". I have to say it is not very newbie friendly. It does not explain many things clearly. And unfortunately, there is not too much introductory materials available on-line. I do not want to buy a book. For example, I found