[R] YALAQ - Yet Another LApply Question
Greg Snow
Greg.Snow at imail.org
Wed Oct 15 19:51:43 CEST 2008
For the first question, ?str tells us that the str function does not return anything, but has a side effect of printing information to the console. So in version 1 when you call the cat function it evaluates its arguments and as it evaluates str(...) the information is printed, then nothing is passed into cat which then prints the name of the object (after str has done its printing). In the second version cat finishes printing the name before str is called so that it is in the correct order.
You might prefer to use lapply/sapply to create a list with all the pieces of interest, then just do str on the resulting list, or look at the TkListView function in the TeachingDemos package for another way to look at the structure of a list.
For example:
TkListView( sapply( ls(pattern='bn'), function(y) get(y), simplify=FALSE, USE.NAMES=TRUE ) )
For the 2nd question, the difference is that the summary function does not print anything, just returns the summary information. When you type summary at the command line the parser automatically calls the print method for the summary object returned, but within functions/loops/apply the summary object is returned (included in the output of lapply) but not printed. You need to explicitly print the results of summary.
Hope this helps,
--
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Thompson, David (MNR)
> Sent: Wednesday, October 15, 2008 10:19 AM
> To: r-help at r-project.org
> Subject: Re: [R] YALAQ - Yet Another LApply Question
>
> Please forgive this repost, it's been a week without a squeak. No
> comments?
>
> Original post:
> https://stat.ethz.ch/pipermail/r-help/2008-October/176340.html
> Hello,
>
> Two lapply questions (system info and sample data below):
>
> 1) Why does the first form of command1 add the name of y _after_ the
> str() output rather than before as does the second (preferred) form?
> # command1 version1
> invisible(lapply(ls(pattern='bn'), function(y) cat(y, "\n",
> str(get(y)), "\n") ))
>
> # command1 version2 (preferred output)
> invisible(lapply(ls(pattern='bn'), function(y) { cat(y, "\n") ;
> str(get(y)) ; cat("\n") } ))
>
> 2) Why does the same method as command1 version2 above not work with
> the
> summary() command as does the second (preferred) set of commands?
> # command2 version1
> lapply(ls(pattern='bn'), function(y) { cat(y, "\n") ;
> summary(get(y))
> ; cat("\n") } )
>
> # command2 version2 (preferred output)
> smry.list <- lapply(ls(pattern='bn'), function(y) summary(get(y)))
> names(smry.list) <- ls(pattern='bn')
> smry.list
>
> Thanx, DaveT.
>
> ###
> # system info:
> > sessionInfo() ; cat("\n") ; Sys.info()[c(1:3,5)]
> R version 2.7.2 (2008-08-25)
> i386-pc-mingw32
>
> locale:
> LC_COLLATE=English_Canada.1252;LC_CTYPE=English_Canada.1252;LC_MONETARY
> =
> English_Canada.1252;LC_NUMERIC=C;LC_TIME=English_Canada.1252
>
> attached base packages:
> [1] stats graphics grDevices datasets tcltk utils methods
> base
>
> other attached packages:
> [1] debug_1.1.0 mvbutils_1.1.1 lattice_0.17-14 plotrix_2.4-7
> svSocket_0.9-5 TinnR_1.0.2 R2HTML_1.59 Hmisc_3.4-3
>
> loaded via a namespace (and not attached):
> [1] cluster_1.11.11 grid_2.7.2 svMisc_0.9-5 tools_2.7.2
>
> sysname release
> version machine
> "Windows" "XP" "build 2600,
> Service Pack 2" "x86"
> # system info:
> ###
>
> ###
> # sample data
> # dput(ban.nat.1994[sample(row.names(ban.nat.1994), 20),])
> bn94 <- structure(list(oplt = c(18L, 50L, 11L, 16L, 54L, 35L, 45L, 40L,
> 15L, 50L, 38L, 45L, 53L, 15L, 1L, 54L, 33L, 13L, 30L, 21L), tree =
> c(144L,
> 824L, 47L, 525L, 291L, 702L, 717L, 615L, 821L, 551L, 750L, 639L,
> 664L, 813L, 31L, 346L, 689L, 59L, 200L, 658L), bd1 = c(NA, NA,
> 3.6, 3.1, 4.72, 2.03, 2.88, 1.65, 5.39, 3.04, 2.75, 3.06, 2.81,
> 2.78, NA, 6.5, 4.62, 4.76, NA, 2.69), bd2 = c(NA, NA, 3.41, 3.06,
> 4.86, 2.09, 2.78, 1.8, 5.08, 3.26, 2.71, 3.1, 2.87, 2.73, NA,
> 6.6, 4.53, 4.97, NA, 2.81), bd = c(NA, 4.25, 3.51, 3.08, 4.79,
> 2.06, 2.83, 1.72, 5.23, 3.15, 2.73, 3.08, 2.84, 2.76, NA, 6.55,
> 4.58, 4.87, NA, 2.75), ht = c(NA, 20.4, 18.1, 18, 25.8, 13.1,
> 15.7, 4, 16, 14, 12.7, 8.6, 8.1, 16.2, NA, 52.7, 31.7, 23.7,
> NA, 17.6), spr = c(NA_integer_, NA_integer_, NA_integer_, NA_integer_,
> NA_integer_, NA_integer_, NA_integer_, NA_integer_, NA_integer_,
> NA_integer_, NA_integer_, NA_integer_, NA_integer_, NA_integer_,
> NA_integer_, NA_integer_, NA_integer_, NA_integer_, NA_integer_,
> NA_integer_), stat = c(1L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
> 0L, 0L, 0L, 0L, 1L, 0L, 0L, 0L, 1L, 0L), dam = c(NA, 2L, NA,
> NA, NA, NA, NA, 2L, NA, NA, 2L, NA, 1L, NA, NA, NA, 1L, NA, NA,
> NA), com = c("", "from partial data set, tend = 1", "", "", "",
> "", "", "", "", "", "", "", "", "", "", "", "", "", "", "")), .Names =
> c("oplt",
> "tree", "bd1", "bd2", "bd", "ht", "spr", "stat", "dam", "com"
> ), row.names = c(1049L, 2845L, 549L, 884L, 3128L, 1887L, 2432L,
> 2087L, 879L, 2729L, 1990L, 2421L, 3089L, 871L, 3L, 3158L, 1801L,
> 704L, 1653L, 1215L), class = "data.frame")
>
> # dput(ban.nat.1995[sample(row.names(ban.nat.1995), 20),])
> bn95 <- structure(list(oplt = c(2L, 27L, 54L, 8L, 8L, 51L, 3L, 4L, 20L,
> 35L, 15L, 22L, 31L, 7L, 4L, 31L, 34L, 6L, 20L, 51L), tree = c(773L,
> 308L, 331L, 234L, 235L, 170L, 211L, 701L, 745L, 709L, 798L, 350L,
> 207L, 736L, 718L, 240L, 193L, 266L, 735L, 244L), bd1 = c(8.41,
> NA, 6.93, 2.74, 6.06, 2.36, 5.87, 3.53, 2.48, NA, 9, 4.18, 1.74,
> 3.42, 5.54, 3.74, 3.26, 2.38, 4.42, 3.65), bd2 = c(8.76, NA,
> 7.17, 2.82, 6.16, 2.33, 6.05, 2.58, 2.5, NA, 9.04, 4.22, 1.68,
> 3.39, 5.52, 3.68, 3.18, 2.38, 4.47, 3.74), bda = c(8.59, NA,
> 7.05, 2.78, 6.11, 2.34, 5.96, 3.05, 2.49, NA, 9.02, 4.2, 1.71,
> 3.41, 5.53, 3.71, 3.22, 2.38, 4.44, 3.7), ht = c(69.2, NA, 55.2,
> 25.7, 47.8, 17.1, 35.6, 11, 12, NA, 52.5, 33.2, 10.4, 16.2, 32.7,
> 22.1, 15, 13.6, 24.5, 22.4), spr = c(NA_integer_, NA_integer_,
> NA_integer_, NA_integer_, NA_integer_, NA_integer_, NA_integer_,
> NA_integer_, NA_integer_, NA_integer_, NA_integer_, NA_integer_,
> NA_integer_, NA_integer_, NA_integer_, NA_integer_, NA_integer_,
> NA_integer_, NA_integer_, NA_integer_), stat = c(0L, 1L, 0L,
> 0L, 0L, 0L, 0L, 0L, 0L, 1L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
> 0L), dam = c(NA, NA, NA, NA, NA, NA, NA, 1L, NA, NA, NA, NA,
> NA, NA, NA, NA, NA, NA, NA, NA), com = c("", "", "", "", "",
> "", "", "", "", "", "", "", "", "", "", "", "", "", "", "")), .Names =
> c("oplt",
> "tree", "bd1", "bd2", "bda", "ht", "spr", "stat", "dam", "com"
> ), row.names = c(34L, 462L, 724L, 227L, 228L, 673L, 76L, 123L,
> 368L, 632L, 281L, 391L, 495L, 199L, 140L, 528L, 604L, 191L, 358L,
> 689L), class = "data.frame")
>
> # dput(ban.nat.1996[sample(row.names(ban.nat.1996), 20),])
> bn96 <- structure(list(oplt = c(23L, 33L, 22L, 19L, 27L, 3L, 27L, 19L,
> 48L, 31L, 54L, 37L, 42L, 45L, 51L, 51L, 27L, 44L, 22L, 33L),
> tree = c(616L, 709L, 426L, 233L, 441L, 213L, 411L, 231L,
> 714L, 206L, 355L, 638L, 266L, 201L, 345L, 298L, 151L, 374L,
> 571L, 708L), bd1 = c(4.68, 1.92, 4.89, 4.88, 2.02, 4.2, 2,
> 2.85, 3.38, 2.48, 3.42, NA, 2.1, 2.05, 1.98, 2.26, NA, 5.16,
> 2.9, 2.32), bd2 = c(4.7, 1.98, 4.94, 5.14, NA, 3.96, NA,
> 2.9, 3.2, 2.42, 3.36, NA, 2, 2.02, NA, NA, NA, 5.2, 2.8,
> 2.24), bd = c(4.69, 1.95, 4.92, 5.01, NA, 4.08, NA, 2.88,
> 3.29, 2.45, 3.39, NA, 2.05, 2.03, NA, NA, NA, 5.18, 2.85,
> 2.28), ht = c(31.9, 14.7, 30.7, 24.2, 9.5, 24.3, 8.2, 28.1,
> 22.5, 10.6, 35.5, NA, 13.3, 9.3, 20.2, 10, NA, 24.7, 18.5,
> 15.7), spr = c(NA, NA, NA, 2L, NA, NA, NA, NA, NA, NA, NA,
> NA, NA, NA, NA, NA, NA, NA, NA, NA), stat = c(0L, 0L, 0L,
> 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 1L, 0L, 0L, 0L, 0L, 1L, 0L,
> 0L, 0L), dam = c(NA, NA, NA, NA, NA, NA, NA, NA, NA, NA,
> NA, NA, NA, NA, NA, NA, NA, 2L, NA, NA), yrc = c(95L, 95L,
> 95L, 95L, 93L, 95L, 93L, 95L, 94L, 95L, 95L, 95L, 94L, 96L,
> 93L, 93L, 95L, NA, 95L, 95L), az = c(NA, 172L, NA, NA, 276L,
> NA, 243L, NA, 221L, 2L, 80L, 270L, 342L, NA, 240L, 170L,
> 6L, NA, NA, 155L), dist = c(NA, 11.21, NA, NA, 8.1, NA, 15.94,
> NA, 9.11, 9.23, 6.39, 6.45, 10.88, NA, 12.42, 15.19, 15.16,
> NA, NA, 13.52), com = c("", "", "", "", "", "", "", "", "",
> "", "", "", "", "", "", "", "", "new", "", "")), .Names = c("oplt",
> "tree", "bd1", "bd2", "bd", "ht", "spr", "stat", "dam", "yrc",
> "az", "dist", "com"), row.names = c(366L, 758L, 335L, 285L, 600L,
> 61L, 583L, 283L, 1184L, 671L, 1422L, 818L, 930L, 1006L, 1331L,
> 1299L, 447L, 996L, 343L, 757L), class = "data.frame")
> # sample data
> ###
>
> *************************************
> Silviculture Data Analyst
> Ontario Forest Research Institute
> Ontario Ministry of Natural Resources
> david.john.thompson at ontario.ca
> http://ontario.ca/ofri
>
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