When reshaping a dataframe in which there are unused factor levels in the id
variable, I get the following error:
Error in if (!all(really.constant)) warning(gettextf("some constant variables
(%s) are really varying", :
missing value where TRUE/FALSE needed
For example,
> df <- data.frame(i = factor(rep(1:5, each = 2)), t = factor(rep(1:2, 5)), x =
> rep(rbinom(5, 1, 0.5), each = 2), y = rpois(10, 10))
> subdf <- subset(df, i %in% 1:3)
defines a dataframe, and a subframe with some unused factor levels (i = 4, 5).
Then
> reshape(df, v.names = "y", timevar = "t", idvar = "i", direction = "wide")
i x y.1 y.2
1 1 0 13 6
3 2 0 12 5
5 3 0 10 9
7 4 1 9 11
9 5 1 12 8
works fine but
> reshape(subdf, v.names = "y", timevar = "t", idvar = "i", direction = "wide")
Error in if (!all(really.constant)) warning(gettextf("some constant variables
(%s) are really varying", :
missing value where TRUE/FALSE needed
produces the error, which happens during the check to see if the variables
assumed constant are constant. The problem is that reshape searches over all
the levels of the id variable (i in this case) to see if the other variables
(here x) are constant. But there is no x associated with i = 4, 5 in the
smaller dataframe, so
> tapply(subdf$x, subdf$i, function(x) length(unique(x)) == 1)
1 2 3 4 5
TRUE TRUE TRUE NA NA
produces some NAs. A slight change to the reshape code to work around this
problem would be to use (the equivalent of)
> tapply(subdf$x, subdf$i[, drop = TRUE], function(x) length(unique(x)) == 1)
1 2 3
TRUE TRUE TRUE
in the reshapeWide function within reshape, but perhaps there is a good reason
not to do this?
Daniel
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