search for: fundtion

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,...

...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

...for there more general idea. help is a very interesting and useful function. However, I would say the content lacks some general idea. I used to learn Mathematica, which is also a high-level tool by their help. It is very comprehensive, yet well-organized with some general idea, some specific fundtion explanation and some functions about one topic. For R's help, you get only the specific explanation for the perticular function, and no more related things. I feel it is more like a reference for experienced user instead of some newbie. I know there should be some trick by R with some dens...