[R] assign()ing within apply

[Thompson, David (MNR)]

Hello,

I'm trying to convert a character column in several dataframes to lower
case.

###
#
# Sample data and 'spp' column summaries:
# dput(ban.ovs.1993[sample(row.names(ban.ovs.1993), 20), 1:4])
ban.ovs.93 <- structure(list(oplt = c(43L, 43L, 38L, 26L, 35L, 8L, 39L,
1L, 
34L, 50L, 10L, 29L, 31L, 24L, 18L, 12L, 27L, 49L, 28L, 51L), 
    rplt = 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_), tree = c(427L, 410L, 639L, 494L, 649L, 166L, 
    735L, 163L, 120L, 755L, 612L, 174L, 129L, 331L, 269L, 152L, 
    552L, 227L, 243L, 96L), spp = c("MH", "MST", "MH", "HE", 
    "BE", "MH", "MH", "MH", "MH", "Or", "IW", "Or", "MH", "MH", 
    "BY", "MH", "MH", "BE", "MH", "MR")), .Names = c("oplt", 
"rplt", "tree", "spp"), row.names = c(4587L, 4570L, 3947L, 2761L, 
3653L, 652L, 4136L, 64L, 3567L, 5318L, 838L, 3091L, 3366L, 2423L, 
1775L, 1061L, 2893L, 5161L, 2967L, 5395L), class = "data.frame")

# dput(pem.ovs.1994[sample(row.names(pem.ovs.1994), 20), 1:4])
pem.ovs.94 <- structure(list(oplt = c(8L, 17L, 36L, 9L, 31L, 11L, 35L,
51L, 
51L, 49L, 40L, 1L, 9L, 17L, 4L, 42L, 6L, 3L, 39L, 25L), tree = c(531L, 
557L, 546L, 261L, 592L, 134L, 695L, 933L, 945L, 114L, 34L, 54L, 
549L, 574L, 193L, 96L, 70L, 4L, 546L, 789L), spp = c("MH", "MH", 
"MH", "BF", "BF", "MH", "IW", "OR", "OR", "BF", "MH", "IW", "OR", 
"MH", "SM", "BE", "BE", "BE", "OR", "OR"), oaz = c(38L, 205L, 
140L, 277L, 329L, 209L, 222L, 24L, 67L, 187L, 156L, 181L, 174L, 
248L, 42L, 279L, 273L, 357L, 160L, 183L)), .Names = c("oplt", 
"tree", "spp", "oaz"), row.names = c(1204L, 2943L, 5790L, 1616L, 
5063L, 2013L, 5691L, 8188L, 8200L, 7822L, 6302L, 54L, 1698L, 
2960L, 421L, 6690L, 775L, 245L, 6205L, 4121L), class = "data.frame")

# count per spp
invisible(lapply(ls(pat='ovs'), function(y) { cat(y, "\n")  ;
print(summary.factor(get(y)[,'spp'])) ; cat("\n") } ) )
ban.ovs.93 
BE  BY  HE  IW  MH  MR MST  Or 
 2   1   1   1  11   1   1   2 

pem.ovs.94 
BE BF IW MH OR SM 
 3  3  2  6  5  1 
#
###

I have tried variants on the following and cannot remember how to have
the result assign()ed back to the original dataframes.
lapply(ls(pat='ovs'), function(y) { assign(paste(y, "[,'spp']", sep=""),
tolower(get(y)[,'spp'])) } )

I *do* get the expected results:
[[1]]
 [1] "mh"  "mst" "mh"  "he"  "be"  "mh"  "mh"  "mh"  "mh"  "or"  "iw"
"or"  "mh"  "mh"  "by"  "mh"  "mh"  "be"  "mh"  "mr" 

[[2]]
 [1] "mh" "mh" "mh" "bf" "bf" "mh" "iw" "or" "or" "bf" "mh" "iw" "or"
"mh" "sm" "be" "be" "be" "or" "or"

, I just can't remember how to get them back into the original dataframe
objects. Suggestions?

Thanx, DaveT.
*************************************
Silviculture Data Analyst
Ontario Forest Research Institute
Ontario Ministry of Natural Resources
david.john.thompson at ontario.ca
http://ontario.ca/ofri