Faceted bar plot shows wrong counts (ggplot2)

Michael,

Thanks for the pointer to the discussion in the ggplot list. It seems
that the reason of this behaviour of facet_grid() is already known and
being discussed by the developers of ggplot2.

facet_grid() reduces the original data frame with unique() before
applying the stats. ?If the data frame has any other column that
prevents duplicated rows, counts are correctly computed.

E.g.

diamonds25 <- droplevels(diamonds[1:25,]) # Keep all columns

# Everything else as before:
base ?<- ?ggplot(diamonds25, ?aes(fill ?= ?cut)) ?+
?geom_bar(position ?= ?"dodge") ?+
?opts(legend.position ?= ?"none")
?base ?+ ?aes(x ?= ?cut) ?+
?facet_grid(. ?~ ?color)


Helios

El d?a 12/03/2012 a las 20:59, "R. Michael Weylandt"

<michael.weylandt at gmail.com> escribi?:

You get the "good" behavior with

base + aes(x = cut) + facet_wrap(~ color, ncol = 5)

so this seems buggy to me.

If someone here doesn't step forward with more insight, I'd forward

it

to the ggplot list to see if one of the developers there can give an
explanation or possibly make the official call that it's a bug.

There was another report of a possible bug in facet_grid() today

that

could be related:

https://groups.google.com/group/ggplot2/browse_thread/thread/5213ac35da6b36d

4

Michael

On Mon, Mar 12, 2012 at 7:16 AM, Helios de Rosario
<helios.derosario at ibv.upv.es> wrote:

I have encountered a problem with faceted bar plots. I have tried

to

create something like the example explained in the ggplot2 book (see

pp.

126-128):

library(ggplot2)
mpg4 ?<- ?subset(mpg, ?manufacturer ?%in%
c("audi", ?"volkswagen", ?"jeep"))
mpg4$manufacturer ?<- ?as.character(mpg4$manufacturer)
mpg4$model ?<- ?as.character(mpg4$model)

base ?<- ?ggplot(mpg4, ?aes(fill ?= ?model)) ?+
geom_bar(position ?= ?"dodge") ?+
opts(legend.position ?= ?"none")
base ?+ ?aes(x ?= ?model) ?+
facet_grid(. ?~ ?manufacturer)

That example works fine; the bar heights are just the same as the
counts in the table:

table(mpg4[,1:2])
? ? ? ? ?model
manufacturer a4 a4 quattro a6 quattro grand cherokee 4wd gti jetta

new

beetle
?audi ? ? ? ?7 ? ? ? ? ?8 ? ? ? ? ?3 ? ? ? ? ? ? ? ? ?0 ? 0 ? ? 0
? ?0
?jeep ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ? ? ? ? ?8 ? 0 ? ? 0
? ?0
?volkswagen ?0 ? ? ? ? ?0 ? ? ? ? ?0 ? ? ? ? ? ? ? ? ?0 ? 5 ? ? 9
? ?6
? ? ? ? ?model
manufacturer passat
?audi ? ? ? ? ? ?0
?jeep ? ? ? ? ? ?0

But in other cases this does not occur. For instance, take a small
subset of data(diamonds):

diamonds25 <- droplevels(diamonds[1:25,2:3])
table(diamonds25)
? ? ? ? ? color
cut ? ? ? ? E F H I J
?Fair ? ? ?1 0 0 0 0
?Good ? ? ?1 0 0 1 4
?Very Good 1 0 3 1 4
?Premium ? 3 1 0 1 0
?Ideal ? ? 1 0 0 1 2

And change the variables mapped in the previous plot:

base ?<- ?ggplot(diamonds25, ?aes(fill ?= ?cut)) ?+
geom_bar(position ?= ?"dodge") ?+
opts(legend.position ?= ?"none")
base ?+ ?aes(x ?= ?cut) ?+
facet_grid(. ?~ ?color)

I see all bars with height = 1.
I have ovserved this problem (wrong bar heights, but not always =

1),

in other cases when all counts are very small or zero.
What's wrong here?

Regards,
Helios

sessionInfo()
R version 2.14.2 (2012-02-29)
Platform: i386-pc-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=Spanish_Spain.1252 ?LC_CTYPE=Spanish_Spain.1252
[3] LC_MONETARY=Spanish_Spain.1252 LC_NUMERIC=C
[5] LC_TIME=Spanish_Spain.1252

attached base packages:
[1] stats ? ? graphics ?grDevices utils ? ? datasets ?methods

base

other attached packages:
[1] ggplot2_0.9.0

loaded via a namespace (and not attached):
?[1] colorspace_1.1-1 ? dichromat_1.2-4 ? ?digest_0.5.1
grid_2.14.2
?[5] MASS_7.3-17 ? ? ? ?memoise_0.1 ? ? ? ?munsell_0.3
plyr_1.7.1
?[9] proto_0.3-9.2 ? ? ?RColorBrewer_1.0-5 reshape2_1.2.1
scales_0.2.0
[13] stringr_0.6



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