How to perfectly align an unequal number of plots (ggplot2,gridExtra)

Question

I would like to perfectly align these plots :

Here is the R code :

library(tidyverse)
library(gridExtra)
groupes <- tribble(~type, ~group, ~prof, ~var,
                   1,1,1,12,
                   1,1,2,-24,
                   1,2,1,-11,
                   1,2,2,7,
                   2,1,1,10,
                   2,1,2,5,
                   2,2,1,-25,
                   2,2,2,2,
                   2,3,1,10,
                   2,3,2,3,
                   3,1,1,10,
                   3,1,2,-5,
                   3,2,1,25,
                   3,2,2,2,
                   3,3,1,-10,
                   3,3,2,3,
                   3,4,1,25,
                   3,4,2,-18)


hlay <- rbind(c(1,2,3),
              c(1,2,3),
              c(NA,2,3),
              c(NA,NA,3))

p1 <-  groupes %>% filter(type==1) %>% ggplot(aes(prof,var)) + geom_col() + facet_wrap(~group,ncol=1) +
  coord_cartesian(ylim=c(-25,25)) +
  labs(title="type 1",x="",y="")
p2 <-  groupes %>% filter(type==2) %>% ggplot(aes(prof,var)) + geom_col() + facet_wrap(~group,ncol=1) +
  coord_cartesian(ylim=c(-25,25)) +
  labs(title="type 2",x="",y="")
p3 <-  groupes %>% filter(type==3) %>% ggplot(aes(prof,var)) + geom_col() + facet_wrap(~group,ncol=1) +
  coord_cartesian(ylim=c(-25,25)) +
  labs(title="type 3",x="",y="")
grid.arrange(p1,p2,p3, layout_matrix=hlay)

I may succeed to produce a better alignment by adding heights=c(1.3,1,1,1) into grid.arrange but that is not a perfect solution. Another solution would be not to take into account the space taken by the labels, but I do not know how to do that.

Redemption

Answer 1

it's probably more manageable if you can set an absolute panel size (and size the device accordingly).

justify <- function(x, hjust="center", vjust="center"){
  w <- sum(x$widths)
  h <- sum(x$heights)
  xj <- switch(hjust,
               center = 0.5,
               left = 0.5*w,
               right=unit(1,"npc") - 0.5*w)
  yj <- switch(vjust,
               center = 0.5,
               bottom = 0.5*h,
               top=unit(1,"npc") - 0.5*h)
  x$vp <- viewport(x=xj, y=yj)
  return(x)
}

library(grid)
gl <- lapply(list(p1,p2,p3),egg::set_panel_size, height=unit(1,"in"))
gl <- lapply(gl, justify, vjust="top")
gridExtra::grid.arrange(grobs=gl, nrow=1)

Honkytonk

Thank you very much. It nearly works ! It works perfectly if the panel-strips are nearly similar. But if the dataset contains letters, in many cases, it will not work. – Redemption

See: groupes <- tribble(~type, ~group, ~prof, ~var, 1,"Aa",1,12, 1,"Aa",2,-24, 1,"Bb",1,-11, 1,"Bb",2,7, 2,"Ég",1,10, 2,"Ég",2,5, 2,"Yg",1,-25, 2,"Yg",2,2, 2,"Ab",1,10, 2,"Ab",2,3, 2,"Cc",1,8, 3,"Dd",1,10, 3,"Dd",2,-5, 3,"Ff",1,-10, 3,"Ff",2,3) – Redemption

You could try changing your theme to make the strip size bigger: https://mcmap.net/q/633492/-edit-strip-size-ggplot2. This way it would not have to change the header size to fit the accents on the letters. – Billiot

Answer 2

Thanks to @user9471246 I managed to create a working solution. The main problem was solved by @user9471246 and then a secondary problem emerged : the height of the "panel-strip" changed as a function of the height of the characters (for example, if the panel title is "aaa" the panel-strip will be shorter than is the panel title is "Égo", because the panel-strips are drawn independently from each other). My solution is to get rid of the panel-strip and to move the panel title into the plot.

library(tidyverse)
library(gridExtra)
library(grid)
# it also requires the "egg" package
groupes <- tribble(~type, ~group, ~prof, ~var,
                   1,"Aa",1,12,
                   1,"Aa",2,-24,
                   1,"Bb",1,-11,
                   1,"Bb",2,7,
                   1,"Cc",1,12,
                   1,"Cc",2,-5,
                   2,"Ég",1,10,
                   2,"Ég",2,5,
                   2,"Yg",1,-25,
                   2,"Yg",2,2,
                   2,"Ab",1,10,
                   2,"Ab",2,3,
                   2,"Cc",1,8,
                   2,"Cc",2,25,
                   3,"Dd",1,10,
                   3,"Dd",2,-5,
                   3,"Ee",1,25,
                   3,"Ee",2,2,
                   3,"Ff",1,-10,
                   3,"Ff",2,3,
                   3,"Ii",1,25,
                   3,"Ii",2,-18,
                   3,"Ll",1,20,
                   3,"Ll",2,-20)


dat_text <- groupes %>% distinct(type, group)



p1 <-  groupes %>% filter(type==1) %>% ggplot(aes(prof,var)) + geom_col() + facet_wrap(~group,ncol=1) +
  coord_cartesian(ylim=c(-25,25)) +
  geom_text(data=filter(dat_text,type==1), aes(x = Inf, y = Inf, label=group), hjust = 1, vjust = 1.05) +
  labs(title="type 1",x="",y="") +
  theme(strip.text.x = element_blank())
p2 <-  groupes %>% filter(type==2) %>% ggplot(aes(prof,var)) + geom_col() + facet_wrap(~group,ncol=1) +
  coord_cartesian(ylim=c(-25,25)) +
  geom_text(data=filter(dat_text,type==2), aes(x = Inf, y = Inf, label=group), hjust = 1, vjust = 1.05) +
  labs(title="type 2",x="",y="") +
  theme(strip.text.x = element_blank())
p3 <-  groupes %>% filter(type==3) %>% ggplot(aes(prof,var)) + geom_col() + facet_wrap(~group,ncol=1) +
  coord_cartesian(ylim=c(-25,25)) +
  geom_text(data=filter(dat_text,type==3), aes(x = Inf, y = Inf, label=group), hjust = 1, vjust = 1.05) +
  labs(title="type 3",x="",y="") +
  theme(strip.text.x = element_blank())



justify <- function(x, hjust="center", vjust="center"){
  w <- sum(x$widths)
  h <- sum(x$heights)
  xj <- switch(hjust,
               center = 0.5,
               left = 0.5*w,
               right=unit(1,"npc") - 0.5*w)
  yj <- switch(vjust,
               center = 0.5,
               bottom = 0.5*h,
               top=unit(1,"npc") - 0.5*h)
  x$vp <- viewport(x=xj, y=yj)
  return(x)
}


gl <- lapply(list(p1,p2,p3),egg::set_panel_size, height=unit(1.95,"in"), width=unit(2.15,"in"))
gl <- lapply(gl, justify, vjust="top")

gridExtra::grid.arrange(grobs=gl, nrow=1)

Redemption