How to end y axis on a tick mark on faceted plots?

Question

I am making several plots from a data frame using facet_wrap. My issue is with formatting the y axis. I am using pretty_breaks in scale_y_continuous to equally space the ticks on the y axis. I would now want to end the y axis on a tick as well and it doesn't seem straight forward as my plots are facetted.

So, what I have: enter image description here

What I want: enter image description here

Hope this makes sense! Thanks for your help

Here is the data:

   ID Age Sex Genotype  Organ Weight Ratio
35  1 P22   F        b   Body    9.2  1.00
36  1 P22   F        b  Heart   78.4  8.52
37  1 P22   F        b   Lung  156.2 16.98
38  1 P22   F        b  Liver  492.1 53.49
39  1 P22   F        b Spleen   44.9  4.88
40  1 P22   F        b  Brain  313.2 34.04
41  2 P22   F        a   Body    9.3  1.00
42  2 P22   F        a  Heart   69.3  7.45
43  2 P22   F        a   Lung  225.6 24.26
44  2 P22   F        a  Liver  512.3 55.09
45  2 P22   F        a Spleen   69.1  7.43
46  2 P22   F        a  Brain  373.2 40.13

Here is the code:

# Load file and find names
df <- read.csv('yaxis_ticks_data.csv')

# Subsetting to remove Body ratio
organ.ratios <- subset(df, df$Organ != 'Body')

## P22 Ratio plots

# Grouping for geom_point
pointGroup <- group_by(organ.ratios, Organ, Genotype, ID, Ratio)
pointGroup.Summary <- summarise(pointGroup,
                            n = n())
pointGroup.Summary

# Grouping for geom_bar
barGroup <- group_by(pointGroup.Summary, Organ, Genotype)
barGroup
barGroup.Summary <- summarise(barGroup,
                          mean_Ratio = mean(Ratio),
                          n = n())
barGroup.Summary

# Plot
P22.Organ.Body.plot <- ggplot() +
geom_bar(data = barGroup.Summary, 
       aes(x = barGroup.Summary$Genotype,
           y = barGroup.Summary$mean_Ratio,
           colour = Genotype,
           fill = Genotype),  
       position = position_dodge(width = 0.9), 
       stat = 'identity',
       show.legend = T) +
geom_point(data = pointGroup.Summary, 
         aes(x = pointGroup.Summary$Genotype, 
             y = pointGroup.Summary$Ratio, 
             colour = Genotype), 
         position = position_jitterdodge(jitter.width = 0.2, dodge.width = 0.9), 
         stat = 'identity', 
         show.legend = FALSE) +
facet_wrap(~Organ, scales = 'free', nrow = 1) +
xlab(expression(bold('Genotype'))) +
ylab(expression(bold('Organ/Body Ratio'))) +
theme(axis.line = element_line(colour = 'black'),
    strip.background = element_blank(),
    strip.text = element_text(face = 'bold'),
    axis.text.x = element_blank(),
    axis.ticks.x = element_blank(),
    panel.grid.major = element_blank(),
    panel.grid.minor = element_blank(), 
    panel.border = element_blank(),
    panel.background = element_blank(),
    legend.text.align = 0,
    legend.title = element_text(face = 'bold'),
    text = element_text(family = 'Arial', size = 14)) +
 scale_color_manual('Genotype', 
                 labels = c('a', 'b'), 
                 values = c('black', 'black')) +
 scale_fill_manual('Genotype', 
                labels = c('a', 'b'), 
                values = c('white', 'deepskyblue3')) +
 scale_y_continuous(breaks = pretty_breaks(), expand = expand_scale(mult = c(0, 0.1)))


#Get plot
P22.Organ.Body.plot

This is actually a question I have myself. I've seen suggested using `scale_y_continuous(limits = c(0, NA)`, but that hasn't worked on facets for me. To improve your question, you should provide some data and code, for a [good reproducible answer](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example). — Anonymous coward, Apr 12 '18 at 15:47
Thanks, I tried that and it hasn't worked either, I'll edit the post with data and code in a minute. — Raphael C, Apr 12 '18 at 16:12

score 0 · Accepted Answer · answered May 13 '18 at 04:05

Here's a simple implementation to calculate the value of the desired y-axis tick for each facet:

library(scales)
library(dplyr)

df.2 <- df %>%
  filter(Organ != "Body") %>%
  select(Genotype, Organ, Ratio) %>%
  group_by(Organ) %>%
  mutate(max.y.tick = max(pretty_breaks()(c(0, Ratio)))) %>%
  ungroup()

> df.2
# A tibble: 10 x 4
   Genotype  Organ Ratio max.y.tick
     <fctr> <fctr> <dbl>      <dbl>
 1        b  Heart  8.52         10
 2        b   Lung 16.98         25
 3        b  Liver 53.49         60
 4        b Spleen  4.88          8
 5        b  Brain 34.04         50
 6        a  Heart  7.45         10
 7        a   Lung 24.26         25
 8        a  Liver 55.09         60
 9        a Spleen  7.43          8
10        a  Brain 40.13         50

This value can then be passed to each facet of the ggplot object via geom_blank():

ggplot(df.2, 
       aes(x = Genotype, y = Ratio, fill = Genotype)) +
  geom_col() +
  geom_point(show.legend = FALSE) +
  scale_y_continuous(breaks = pretty_breaks(),
                     expand = c(0, 0)) +
  geom_blank(aes(y = max.y.tick)) +
  facet_wrap(~Organ, scales = "free_y", nrow = 1)

(I skipped all the theme / label components, as they are irrelevant to the crux of the question.)

How to end y axis on a tick mark on faceted plots?

1 Answers1