Re: [R] How to extract same columns from identical dataframes in a list?

On 10 Feb 2016, at 10:04 , Wolfgang Waser wrote: > Hi, > > sapply(l,"[",T,2) > > and > > sapply(l, function(e) e[, 2]) > > > work fine! > > > Thanks a lot! > > Why is the second version "brute force and ignorance"? Is one of the > versions to be preferred? If

Re: [R] How to extract same columns from identical dataframes in a list?

Google! (e.g. on "R Language tutorials") Some specific recommendations can be found here: https://www.rstudio.com/resources/training/online-learning/#R Cheers, Bert Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka

Re: [R] How to extract same columns from identical dataframes in a list?

Hi, sapply(l,"[",T,2) and sapply(l, function(e) e[, 2]) work fine! Thanks a lot! Why is the second version "brute force and ignorance"? Is one of the versions to be preferred? If so, which and why (very briefly, please)? Results of the other options mentioned: > sapply(l,"[[",2)

Re: [R] How to extract same columns from identical dataframes in a list?

ow to extract same columns from identical dataframes in a > list? > > Hi, > > sorry if my description was too short / unclear. > > > I have a list of 7 data frames, each data frame having 24 rows (hour > > of the day) and 5 columns (weeks) with a total of 5 x 24 values

Re: [R] How to extract same columns from identical dataframes in a list?

Hi, sorry if my description was too short / unclear. > I have a list of 7 data frames, each data frame having 24 rows (hour of > the day) and 5 columns (weeks) with a total of 5 x 24 values [1] week1 week2 week3 ... 1 x a m ... 2 y b n 3

Re: [R] How to extract same columns from identical dataframes in a list?

Hi Wolfgang, If you use cbind in the do.call you get something close to what you want. You can then use grep to get just the columns you are interested in (I assume they all have the same name in the original data.frames) dfa <- data.frame(cola = c(6:10), colb = c(1:5), colc = c(11:15)) dfb <-

Re: [R] How to extract same columns from identical dataframes in a list?

Like this? > l <- replicate(3,data.frame(w1=sample(1:4),w2=sample(1:4)), simplify=FALSE) > l [[1]] w1 w2 1 2 2 2 3 3 3 1 1 4 4 4 [[2]] w1 w2 1 3 4 2 2 2 3 1 3 4 4 1 [[3]] w1 w2 1 1 4 2 4 3 3 2 1 4 3 2 > sapply(l,"[[",2) [,1] [,2] [,3] [1,]244 [2,]

Re: [R] How to extract same columns from identical dataframes in a list?

Or do.call( rbind, list.of.df ) from base R (without some of the robust behaviors that ldply implements). -- Sent from my phone. Please excuse my brevity. On February 8, 2016 7:33:54 AM PST, Ulrik Stervbo wrote: >Hi Wolfgang, > >I'm not sure exactly what you want,

Re: [R] How to extract same columns from identical dataframes in a list?

Hi, Although you did not provide any reproducible example, it seems you store the same type of values in your data.frames. If this is true, it is much more efficient to store your data in an array: mylist <- list(a = data.frame(week1 = rnorm(24), week2 = rnorm(24)), b =

[R] How to extract same columns from identical dataframes in a list?

Hello, I have a list of 7 data frames, each data frame having 24 rows (hour of the day) and 5 columns (weeks) with a total of 5 x 24 values I would like to combine all 7 columns of week 1 (and 2 ...) in a separate data frame for hourly calculations, e.g. > apply(new.data.frame,1,mean) In some

Re: [R] How to extract same columns from identical dataframes in a list?

Hi Wolfgang, I'm not sure exactly what you want, but the ldply in the package plyr can help you make a data.frame from a list of data.frames: library(plyr) dfa <- data.frame(cola = LETTERS[1:5], colb = c(1:5)) dfb <- data.frame(cola = LETTERS[1:5], colb = c(1:5)) df.lst <- list(dfa.name = dfa,