On Wed, 22 Feb 2006, Daniel Farewell wrote:
> 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
Yes, I think it's a bug. Thanks for pointing it out.
-thomas
>
> 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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>
Thomas Lumley Assoc. Professor, Biostatistics
[EMAIL PROTECTED] University of Washington, Seattle
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