How can I draw geom_line across facets or grid

Question

My data :

Plate   Month   Day     Concentration
A       April   1       17.1094
B       April   2       16.001
C       April   3       17.9501
D       April   4       18.3686
E       April   5       18.3133
F       April   6       19.1189
G       May     1       16.0423
H       May     2       16.3614
I       May     3       18.5723
J       May     4       19.1091
K       May     5       17.6863
L       May     6       18.2647

Using geom_line I was able to draw a line graph connecting all dots in a nice plot as follows :

myData <- data.frame(read.table("myData.txt", sep="\t", header=TRUE))

ggplot(myData, aes(x = Plate, y = Concentration, group=1)) + geom_point() + geom_line()

I differentiated data based on Month using facet panels, and then draw a line graph as follows. Here, the line plot is disconnected after the last day in April month. How can I draw line plot that draws across facets i.e. from April to May ?

ggplot(myData, aes(x = Day, y = Concentration)) + facet_wrap(~ Month, nrow = 1) + geom_line() + geom_point()

Facets are separate graphs. Seems like you don't want facets... — Gregor Thomas, Mar 09 '21 at 20:00
if I don't use facets, how can I represent/label Months data April vs May in my graph ? — srg, Mar 09 '21 at 20:03
It appears like R ggplot does not offer a solution to draw continuos line graph and differentiate/label/group data on x-axis ? — srg, Mar 09 '21 at 20:39

score 1 · Answer 1 · answered Mar 09 '21 at 21:19

You could fake it:

mydata <- "Plate   Month   Day     Concentration
A       April   1       17.1094
B       April   2       16.001
C       April   3       17.9501
D       April   4       18.3686
E       April   5       18.3133
F       April   6       19.1189
G       May     1       16.0423
H       May     2       16.3614
I       May     3       18.5723
J       May     4       19.1091
K       May     5       17.6863
L       May     6       18.2647"

myData <- data.frame(read_table(mydata))

myData <- myData %>% mutate(plot_day = seq_along(Day))
rect_data <- myData %>% group_by(Month) %>% 
  summarise(data.frame(xmin = min(plot_day), xmax=max(plot_day))) %>% 
  mutate(ymin = 19.25, ymax=19.5)

ggplot() + 
  geom_point(data = myData, aes(x = plot_day, y = Concentration)) + 
  geom_rect(data=rect_data, aes(ymin=ymin, ymax=ymax, xmin=xmin-c(.55, .45), xmax=xmax+c(.45, .55)), 
            fill="gray75", col="transparent") + 
  geom_text(data = rect_data, aes(x=c(3.5, 9.5), y=19.375, label = c("April", "May"))) + 
  coord_cartesian(xlim=c(.449, 12.551), ylim=c(15.75, 19.501), expand=0) + 
  scale_x_continuous(breaks = seq(2,12, by=2), 
                     labels=c("2", "4", "6", "2", "4", "6")) + 
  geom_vline(xintercept=6.5, col="white", size=2) +
  geom_line(data = myData, aes(x = plot_day, y = Concentration)) + 
  labs(x="Day")

Thank you DaveArmstrong for this temporary solution to make the graph appear like having facets without using any grids. This works for customizing on few plots, but it becomes cumbersome to apply this customization for multiple plots recursively. — srg, Mar 29 '21 at 19:21

How can I draw geom_line across facets or grid

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