All,
I realize from the archive that the sort argument in merge has been subject to
discussion before, though I couldn't find an explanation for this behavior. I
tried to simplify this to (kind of) minimal code from a real example to the
following (and I have no doubts that there are smart people around achieving
the same with smarter code :-)). I'm running R 2.15.1 64bit under MS Windows 7,
full session info below.
I do have a list with two dataframes:
test <- list(structure(list(product = structure(c(1L, 2L, 3L, 4L, 5L,
6L, 1L, 2L, 3L, 4L, 5L, 6L, 1L, 2L, 3L, 4L, 5L, 6L, 1L, 2L, 3L,
4L, 5L, 6L), .Label = c("Y1", "Y2", "G", "F", "L", "K"), class = "factor"),
cong = c(-1, -1, -1, -1, -1, -1, 0, 0, 0, 0, 0, 0, 1, 1,
1, 1, 1, 1, 11, 11, 11, 11, 11, 11), x = c(5.85714285714286,
5.9, 7.3, 5.85714285714286, 7.27272727272727, 4.375, 3.875,
2.5, 4.8, 3.625, 6.25, 4.71428571428571, 3.53571428571429,
4.63888888888889, 4.42424242424242, 4.78260869565217, 4.875,
3.80434782608696, 5.73170731707317, 5.41935483870968, 5.78125,
6.30188679245283, 6.87755102040816, 5.56603773584906)), .Names =
c("product",
"cong", "x"), row.names = c(NA, -24L), class = "data.frame"),
structure(list(product = structure(c(1L, 2L, 3L, 4L, 5L,
6L, 1L, 2L, 3L, 4L, 5L, 6L), .Label = c("Y1", "Y2", "G",
"F", "L", "K"), class = "factor"), cong = c(-1, -1, -1, -1,
-1, -1, 0, 0, 0, 0, 0, 0), x = c(3.04347826086957, 4.18181818181818,
3.75, 4.31578947368421, 4.5, 3.73913043478261, 4.8876404494382,
5.20792079207921, 5.68, 5.70526315789474, 6.38636363636364,
4.96703296703297)), .Names = c("product", "cong", "x"), row.names = c(NA,
-12L), class = "data.frame"))
The dataframes are pretty much the same but for the values in the x-column and
the fact that the second one has only half as many observations, missing the
second half of the expand.grid if you like. Now if I run
lapply(test, function(x) merge(x, expand.grid(product=c("Y1", "Y2", "G", "F",
"L", "K"), cong=c(-1,0,1,11)), all=T, sort=TRUE)) # sort=TRUE is the default,
so could be omitted
sorts the first dataframe according to the labels of factor "product", while
for the second one the order is maintained from the first dataframes (x) to
merge (which is the difference that I could not find being documented). Now I
run the same code with sort=FALSE instead:
lapply(test, function(x) merge(x, expand.grid(product=c("Y1", "Y2", "G", "F",
"L", "K"), cong=c(-1,0,1,11)), all=T, sort=FALSE))
The results are at least consistent and fulfill my needs (this is, btw, not
unexpected from the documentation). Note that I get exactly the same behavior
if I apply merge subsequently to test[[1]] and test[[2]], so it is not an issue
from lapply. (I realize that my dataframes are ordered by levels of product,
but using test[[2]] <- test[[2]][sample(12),] and applying the same code as
above reveals that indeed no sorting is done but the order is maintained from
the first dataframe.)
I have a working solution for myself, so I'm not after any advice on how to
achieve the sorting -- I'd just like to better understand what's going on here
and/or what I might have missed in the documentation or in the list archives.
Thanks in advance,
Michael
Session info:
R version 2.15.1 (2012-06-22)
Platform: x86_64-pc-mingw32/x64 (64-bit)
locale:
[1] LC_COLLATE=German_Germany.1252 LC_CTYPE=German_Germany.1252
LC_MONETARY=German_Germany.1252 LC_NUMERIC=C
LC_TIME=German_Germany.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_2.15.1
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