[Rd] colnames for data.frame could be greatly improved

[Jan Gorecki]

Hi there,
Any update on this?
Should I create bugzilla ticket and submit patch?
Regards
Jan Gorecki

On 20 December 2016 at 01:27, Jan Gorecki <J.Gorecki at wit.edu.pl> wrote:
> Hello,
>
> colnames seems to be not optimized well for data.frame. It escapes
> processing for data.frame in
>
>   if (is.data.frame(x) && do.NULL)
>     return(names(x))
>
> but only when do.NULL true. This makes huge difference when do.NULL
> false. Minimal edit to `colnames`:
>
>     if (is.data.frame(x)) {
>         nm <- names(x)
>         if (do.NULL || !is.null(nm))
>             return(nm)
>         else
>             return(paste0(prefix, seq_along(x)))
>     }
>
> Script and timings:
>
> N=1e7; K=100
> set.seed(1)
> DF <- data.frame(
>     id1 = sample(sprintf("id%03d",1:K), N, TRUE),      # large groups (char)
>     id2 = sample(sprintf("id%03d",1:K), N, TRUE),      # large groups (char)
>     id3 = sample(sprintf("id%010d",1:(N/K)), N, TRUE), # small groups (char)
>     id4 = sample(K, N, TRUE),                          # large groups (int)
>     id5 = sample(K, N, TRUE),                          # large groups (int)
>     id6 = sample(N/K, N, TRUE),                        # small groups (int)
>     v1 =  sample(5, N, TRUE),                          # int in range [1,5]
>     v2 =  sample(5, N, TRUE),                          # int in range [1,5]
>     v3 =  sample(round(runif(100,max=100),4), N, TRUE) # numeric e.g. 23.5749
> )
> cat("GB =", round(sum(gc()[,2])/1024, 3), "\n")
> #GB = 0.397
> colnames(DF) = NULL
> system.time(nm1<-colnames(DF, FALSE))
> #   user  system elapsed
> # 22.158   0.299  22.498
> print(nm1)
> #[1] "col1" "col2" "col3" "col4" "col5" "col6" "col7" "col8" "col9"
>
> ### restart R
>
> colnames <- function (x, do.NULL = TRUE, prefix = "col")
> {
>     if (is.data.frame(x)) {
>         nm <- names(x)
>         if (do.NULL || !is.null(nm))
>             return(nm)
>         else
>             return(paste0(prefix, seq_along(x)))
>     }
>     dn <- dimnames(x)
>     if (!is.null(dn[[2L]]))
>         dn[[2L]]
>     else {
>         nc <- NCOL(x)
>         if (do.NULL)
>             NULL
>         else if (nc > 0L)
>             paste0(prefix, seq_len(nc))
>         else character()
>     }
> }
> N=1e7; K=100
> set.seed(1)
> DF <- data.frame(
>     id1 = sample(sprintf("id%03d",1:K), N, TRUE),      # large groups (char)
>     id2 = sample(sprintf("id%03d",1:K), N, TRUE),      # large groups (char)
>     id3 = sample(sprintf("id%010d",1:(N/K)), N, TRUE), # small groups (char)
>     id4 = sample(K, N, TRUE),                          # large groups (int)
>     id5 = sample(K, N, TRUE),                          # large groups (int)
>     id6 = sample(N/K, N, TRUE),                        # small groups (int)
>     v1 =  sample(5, N, TRUE),                          # int in range [1,5]
>     v2 =  sample(5, N, TRUE),                          # int in range [1,5]
>     v3 =  sample(round(runif(100,max=100),4), N, TRUE) # numeric e.g. 23.5749
> )
> cat("GB =", round(sum(gc()[,2])/1024, 3), "\n")
> #GB = 0.397
> colnames(DF) = NULL
> system.time(nm1<-colnames(DF, FALSE))
> #   user  system elapsed
> #  0.001   0.000   0.000
> print(nm1)
> #[1] "col1" "col2" "col3" "col4" "col5" "col6" "col7" "col8" "col9"
>
> sessionInfo()
> #R Under development (unstable) (2016-12-19 r71815)
> #Platform: x86_64-pc-linux-gnu (64-bit)
> #Running under: Debian GNU/Linux stretch/sid
> #
> #locale:
> # [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
> # [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
> # [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
> # [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
> # [9] LC_ADDRESS=C               LC_TELEPHONE=C
> #[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
> #
> #attached base packages:
> #[1] stats     graphics  grDevices utils     datasets  methods   base  #
> #
> #loaded via a namespace (and not attached):
> #[1] compiler_3.4.0