Question

2 CSV fs: works

    read.table('./Trial7/glob.csv')->e1
    read.table('./Trial7/keh.csv')->e2
    b1<-data.frame(as.Date(e1$V1, "%d.%m.%Y"), e1$V2)
    b2<-data.frame(as.Date(e2$V1, "%d.%m.%Y"), e2$V2)

    png('./Pictures/compare2.png')
    plot(b1, type='l', ylim=range(b1[2],b2[2]))
    lines(b2)

    dev.off()

General case: not working

    trial_files<-Sys.glob('./Trial7/*.csv')

    lapply(trial_files, read.table)->e
    b<-data.frame(as.Date(e$V1, "%d.%m.%Y"), e$V2)   ## ERR? (1)
    png('./Pictures/compareMany.png')
    plot(b[1], type='l', ylim=range(b[,2]))          ## ERR? (2)
    lines(b[2])                                      ## Not general, have to 
                                                     ## solve 1/2 first

    dev.off()

I find it hard to explain this without Pythonic list-comprehensions so I want:

[data.frame(as.Date(ee$V1, "%d.%m.%Y"), ee$V2) for ee in e]

…now with R, some lapply(...) or how to do this list-comprehension?

Answer 1

b <- lapply(Sys.glob('Trial7/*.csv'), function(file) {
    e <- read.table(file)
    data.frame(as.Date(e$V1, "%d.%m.%Y"), e$V2)
})

png('./Pictures/compare2.png')
plot(b[[1]], type='l', ylim=range(b[[1]][[2]],b[[2]][[2]]))
lines(b[[2]])