In the plot below, I have a faceted grid.
Is there any way to center both subplots at 0, while keeping different min/max values for the x axis?
In the case below that would be xlim=c(-1,1) for left and xlim=c(-2,2) for right, but it should be generally applicable.
(in a real life example, those are faceted volcano plots and I want to center at 0 effect size but keep the different x scales for different plots)
library(ggplot2) df = data.frame(x=c(1,2), y=c(0,0), group=c(1,2)) ggplot(df, aes(x=x, y=y)) + geom_point() + facet_wrap(~group, scale="free_x") 
5 Answers
Answers 1
I've also needed something like this to display asymmetric spectra side-by-side,
Try this function,
symmetrise_scale <- function(p, axis = "x"){ gb <- ggplot_build(p) type <- switch(axis, "x" = "x.range", "y" = "y.range") lims <- sapply(gb$panel$ranges, "[[", type) fname <- as.character(p$facet$facets) facets <- gb$panel$layout[[fname]] lims2 <- as.vector(t(tcrossprod(apply(abs(lims), 2, max), c(-1,1)))) dummy <- setNames(data.frame(rep(facets, each=2), lims2), c(fname, axis)) switch(axis, "x" = p + geom_blank(data=dummy, aes(x=x, y=Inf), inherit.aes = FALSE), "y" = p + geom_blank(data=dummy, aes(x=Inf, y=y), inherit.aes = FALSE)) } library(ggplot2) df = data.frame(x=c(1,2), y=c(5,0.2), group=c(1,2)) p <- ggplot(df, aes(x=x, y=y)) + geom_point() + facet_wrap(~group, scale="free") symmetrise_scale(p, "x") 
symmetrise_scale(p, "y") 
Answers 2
with version ggplot2_2.2.1.9000
symmetrise_scale <- function(p, axis = "x"){ gb <- ggplot_build(p) type <- switch(axis, "x" = "x.range", "y" = "y.range") fname <- setdiff(names(gb$layout$layout), c("PANEL", "ROW", "COL", "SCALE_X", "SCALE_Y")) facets <- gb$layout$layout[ ,fname, drop=FALSE] lims <- do.call(cbind, lapply(gb$layout$panel_params, "[[", type)) lims2 <- as.vector(t(tcrossprod(apply(abs(lims), 2, max), c(-1,1)))) dummy <- setNames(data.frame(facets[rep(seq_len(nrow(facets)), each=2),], lims2), c(fname, axis)) switch(axis, "x" = p + geom_blank(data=dummy, aes(x=x, y=Inf), inherit.aes = FALSE), "y" = p + geom_blank(data=dummy, aes(x=Inf, y=y), inherit.aes = FALSE)) } Answers 3
A simpler, perhaps more robust solution, would be the following. In a more complex plot using several dataframes you would need a similar geom_blank term for each one.
df = data.frame(x=c(1,2,3,4,5,6), y=c(5,-3,2,-0.2,0.3,-0.1), group=c(1,1,1,2,2,2)) ggplot(df, aes(x=x, y=y)) + geom_blank(aes(y=-y)) + #plot mirror image points invisibly (can do same with x) geom_line() + facet_wrap(~group, scale="free") 
Answers 4
library(ggplot2) library(tidyverse) df = data.frame(x=c(1,2), y=c(0,0), group=c(1,2)) # determine the maximum range df_xr <- df %>% group_by(group) %>% summarize(xr = max(abs(x))) %>% ungroup() # join the mximum range ot original df df_plot <- df %>% inner_join(df_xr) # plot using geom_blank to force the extents without plotting anything ggplot(df_plot, aes(x=x, y=y)) + geom_blank(aes(x = xr)) + geom_blank(aes(x = -xr)) + geom_point() + facet_wrap(~group, scale="free_x") 
Answers 5
This seems to do the trick - for now (this is ggplot2 2.2.1). The main edits to the previous answer are to reflect changes in the names/structure of the ggplot_build object.
symmetrise_scale <- function(p, axis = "x"){ gb <- ggplot_build(p) type <- switch(axis, "x" = "x.range", "y" = "y.range") fname <- setdiff(names(gb$layout$panel_layout), c("PANEL", "ROW", "COL", "SCALE_X", "SCALE_Y")) facets <- gb$layout$panel_layout[ ,fname, drop=FALSE] lims <- do.call(cbind, lapply(gb$layout$panel_ranges, "[[", type)) lims2 <- as.vector(t(tcrossprod(apply(abs(lims), 2, max), c(-1,1)))) dummy <- setNames(data.frame(facets[rep(seq_len(nrow(facets)), each=2),], lims2), c(fname, axis)) switch(axis, "x" = p + geom_blank(data=dummy, aes(x=x, y=Inf), inherit.aes = FALSE), "y" = p + geom_blank(data=dummy, aes(x=Inf, y=y), inherit.aes = FALSE)) } library(ggplot2) df <- data.frame(x=c(1,2,3,4,5,6), y=c(5,-3,2,-0.2,0.3,-0.1), group=c(1,1,1,2,2,2)) p <- ggplot(df, aes(x=x, y=y)) + geom_line() + facet_wrap(~group, scale="free") symmetrise_scale(p, "y") 
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