[R] ggplot2 - unexpected beahviour with facet_grid

[Alain Guillet]

Hello,

I use ggplot2 in order to represent the same data during 3 periods so I 
call facet_grid to get one subgraph by period. But when I do so, I get 
different results between the call on the whole data and the one on only 
one period (I expect to get one of the subgraphs to be identical to the 
graph obtained when using only one period).

I added the code and my session info hereunder. Could you explain me 
what I do worng or if there is a bug? Thank you.

Kind regards,
Alain

------------------------------

library(ggplot2)

# data
tmp <- 
data.frame(x=rnorm(9000),y=rnorm(9000),color=factor(rep(1:3,each=3000)),period=factor(rep(1:3,3000)),ligne=factor(rep(1:2,4500)))

# plot with the three periods
ggplot(tmp,aes(x=x,y=y,col=color,linetype=ligne))+geom_smooth()+scale_colour_manual(values=c("black","blue","yellow"))+guides(linetype=FALSE,col=FALSE)+facet_grid(period~.)

#plot with only the first period
ggplot(tmp[tmp$period=="1",],aes(x=x,y=y,col=color,linetype=ligne))+geom_smooth()+scale_colour_manual(values=c("black","blue","yellow"))+guides(linetype=FALSE,col=FALSE)+facet_grid(period~.)

------------------------------

R version 3.3.1 (2016-06-21)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux 8 (jessie)

locale:
  [1] LC_CTYPE=en_GB.UTF-8       LC_NUMERIC=C LC_TIME=en_GB.UTF-8
  [4] LC_COLLATE=en_GB.UTF-8     LC_MONETARY=en_GB.UTF-8 
LC_MESSAGES=en_GB.UTF-8
  [7] LC_PAPER=en_GB.UTF-8       LC_NAME=C LC_ADDRESS=C
[10] LC_TELEPHONE=C             LC_MEASUREMENT=en_GB.UTF-8 
LC_IDENTIFICATION=C

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

other attached packages:
[1] doBy_4.5-15   ggplot2_2.1.0

loaded via a namespace (and not attached):
  [1] Rcpp_0.12.5      lattice_0.20-33  digest_0.6.9 MASS_7.3-45   
grid_3.3.1
  [6] plyr_1.8.4       nlme_3.1-128     gtable_0.2.0 magrittr_1.5   
  scales_0.4.0
[11] stringi_1.1.1    reshape2_1.4.1   Matrix_1.2-6 labeling_0.3   
  tools_3.3.1
[16] stringr_1.0.0    munsell_0.4.3    colorspace_1.2-6 mgcv_1.8-12


-- 
Alain Guillet
Statistician and Computer Scientist

SMCS - IMMAQ - Université catholique de Louvain
http://www.uclouvain.be/smcs

Bureau c.316
Voie du Roman Pays, 20 (bte L1.04.01)
B-1348 Louvain-la-Neuve
Belgium

Tel: +32 10 47 30 50

Accès: http://www.uclouvain.be/323631.html