Alejandra Lopez-Galan <alejandra7ga...@gmail.com> writes: Hello, I'm not sure to fully answer you question but I'll give it a try. I'll use the library "data.table" as I forgot how to do it in base R. If you don't have it you will have to install it by doing
> install.packages(data.table,repos ="http://cran.us.r-project.org";) let's say you have this list of data.frame > lapply(1:2,function(x) data.frame(B=letters[1:10],A=rnorm(10))) ## [[1]] ## B A ## 1 a 1.8276026 ## 2 b 0.2870562 ## 3 c -0.6304431 ## 4 d 0.3066375 ## 5 e 0.3274438 ## 6 f 0.3370640 ## 7 g -1.6660051 ## 8 h -0.3736336 ## 9 i 0.1494459 ## 10 j -1.0036616 ## [[2]] ## B A ## 1 a -1.1488812 ## 2 b -0.4423796 ## 3 c -0.2690834 ## 4 d -1.1390742 ## 5 e 0.7142574 ## 6 f 0.3316523 ## 7 g 0.3187546 ## 8 h 0.1099996 ## 9 i 0.3972000 ## 10 j 0.4749161 and want to sum the A column for each data.frame then you can use the following: # Assign the list to the variable aa aa <- lapply(1:2,function(x) data.table(B=letters[1:10],A=rnorm(10))) then: > >lapply(aa,function(x) data.table(x)[,sum(A)]) ## [[1]] ## [1] 6.533179 ## [[2]] ## [1] 2.075677 Notice that I converted the each data.frame to a data.table and then sum the column A. If you want to bind the resutls together you can do do.call(rbind,lapply(aa,function(x) data.table(x)[,sum(A)])) [,1] [1,] -9.377476 [2,] -3.853971 HTH, Best Regards, Jeremie > Hi, I am pretty new to R and I would apreciatte very much your help to > solve my problem. I have 40 csv files that have the same structure, and I > want to merge them into a single data frame. > > I already have load and combined all the cvs files into a large list, and I > created two > > filenames <- list.files('data',full.names=TRUE) > > All_data <- lapply(filenames,function(i){ > ###read cvs files and add the row and column names to each data frame### > read.csv(i, header=FALSE, sep = "", col.names = col_names, row.names = > row_names) > }) > > However I would like to sum the rows of cvs files to get a single data > frame (each cvs file has 47 rows and colunms, so the final data frame > should have the same). I could only do it one by one data data frame, but I > was wondering if anyone could give an idea of how to write a function for > this. > > Thanks, > Alejandra > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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 -- To UNSUBSCRIBE and more, see 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.
