how to limit x axis length based on values in all facets of facet_wrap

Question

I have a load of genomic data (dput way too large) Classes ‘grouped_df’, ‘tbl_df’, ‘tbl’ and 'data.frame': 7454 obs. of 3 variables:

 $ chr    : num  1 1 1 1 1 1 1 1 1 1 ...
 $ leftPos: num  480000 600000 2520000 2760000 2880000 3000000 3120000 3480000 3600000 4440000 ...
 $ Means  : num  45.2 58.3 10.7 81.2 16 ...
 - attr(*, "vars")=List of 1
  ..$ : symbol chr
 - attr(*, "labels")='data.frame':  22 obs. of  1 variable:
  ..$ chr: Factor w/ 24 levels "chr1","chr10",..: 1 2 3 4 5 6 7 8 9 10 ...
  ..- attr(*, "vars")=List of 1
  .. ..$ : symbol chr
 - attr(*, "indices")=List of 22
  ..$ : int  0 1 2 3 4 5 6 7 8 9 ...
  ..$ : int  559 560 561 562 563 564 565 566 567 568 ...
  ..$ : int  908 909 910 911 912 913 914 915 916 917 ...
  ..$ : int  1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 ...
  ..$ : int  1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 ...
  ..$ : int  1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 ...
  ..$ : int  2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 ...
  ..$ : int  2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 ...
  ..$ : int  2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 ...
  ..$ : int  2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 ...
  ..$ : int  2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 ...
  ..$ : int  2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 ...
  ..$ : int  3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 ...
  ..$ : int  3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 ...
  ..$ : int  3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 ...
  ..$ : int  3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 ...
  ..$ : int  4521 4522 4523 4524 4525 4526 4527 4528 4529 4530 ...
  ..$ : int  5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 ...
  ..$ : int  5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 ...
  ..$ : int  6251 6252 6253 6254 6255 6256 6257 6258 6259 6260 ...
  ..$ : int  6683 6684 6685 6686 6687 6688 6689 6690 6691 6692 ...
  ..$ : int  7140 7141 7142 7143 7144 7145 7146 7147 7148 7149 ...
 - attr(*, "group_sizes")= int  559 349 383 370 283 229 177 173 140 222 ...
 - attr(*, "biggest_group_size")= int 682

I would like to plot this on a facet plot but limit the x ax-s to the maximum of the leftPos for each chr. At the moment the facet is plotted for each chr with equal width. When I use scales="free_x" the facet just stretches the plot to fill a pre-defined width. Is it possible to have different width facets?

The code I'm using so far:

ggplot(Zoutliers1,aes(x = leftPos,
                         y = as.numeric(Means),
                         group = chr,
                         xend = leftPos,
                         yend=0))+
  geom_bar(stat="identity",fill = "red", size = 1, colour = "red")+
  geom_line()+
  geom_segment(linetype= 1, colour = "#919191")+
  ggtitle(TBBName)+
  ylim(-50,480)+
  facet_wrap(~ chr,nrow = 1)+
  geom_hline(yintercept = UL1)+
  geom_hline(yintercept = LL1)+
  theme(panel.margin = unit(0.1, "lines"))+
  theme(axis.text.x = element_blank())+
  theme(panel.border = element_rect(fill=NA,color="darkred", size=0.5, 
                                    linetype="dashed"))

The plot I'm getting:

Answer 1

You need to set the 'space' parameter to 'free', which can only be done in facet_grid. Here is a demonstration with sample data.

library(gridExtra)
library(ggplot2)

#creating some sample data
set.seed(10001)

dat <-data.frame(chr=1:6,leftPos=seq(100,1000,length.out=6))
dat2 <- dat[sample(1:nrow(dat),1000,T),]
dat2$x <- rnorm(nrow(dat2))*dat2$chr

#basic plot

p1 <- ggplot(dat2, aes(x=x)) +
  geom_histogram() 

#different scales
p_scales <- p1 + facet_grid(.~chr, scales="free_x") + labs(title="free x, default space")
p_space_scales <- p1 + facet_grid(.~chr, scales = "free_x",space="free") + labs(title="free x and free space")


grid.arrange(p_scales,p_space_scales)