fixed_width

align_ggplot.r

library(ggplot2)
library(grid)

p1 <- qplot(1,1000, colour="test", linetype="longer legend") + 
  ylab("double\nline") 
p2 <- qplot(1:10,1:10, colour="test") + 
  ylab("y") + guides(color="none")


## fixed_width <- function(p, width=unit(3, "cm"), draw=FALSE){
##   gt <- ggplot_gtable(ggplot_build(p))
##   panel_index <- gt$layout$r[gt$layout$name=="panel"]
##   gt$widths[[panel_index]] <- width 

##   if(draw) grid.draw(gt)
##   class(gt) <- c(class(gt), "grob")
##   invisible(gt)
## }

## library(gridExtra)
## grid.arrange(fixed_width(p1), fixed_width(p2))

left_width <- function(g){
  axis_l_index <- g$layout$r[g$layout$name=="axis-l"]
  ylab_index <- g$layout$r[g$layout$name=="ylab"]
  g$widths[[axis_l_index]] + g$widths[[ylab_index]]
}

full_width <- function(g){
  sum(g$widths)
}

set_panel_width <- function(g, width=unit(3, "cm")){
  panel_index <- g$layout$r[g$layout$name=="panel"]
  g$widths[[panel_index]] <- width 
  g
}

as.gtable <- function(p)
  ggplot_gtable(ggplot_build(p))

align_plots <- function(..., width=unit(3, "cm")){

  pl <- list(...)
  gl <- lapply(pl, as.gtable)
  gl <- lapply(gl, set_panel_width, width=width)
  
  left <- lapply(gl, left_width)
  max_left <- max(do.call(unit.c, left))

  widths <- lapply(gl, full_width)
  max_width <- max(do.call(unit.c, widths))
  
  lay <- grid.layout(nrow=length(gl), ncol=1)
  vp <- viewport(layout=lay)
  pushViewport(vp)
  
  for(ii in seq_along(gl)){
    pushViewport(viewport(layout.pos.row=ii))
    pushViewport(viewport(x=unit(0.5, "npc") - 0.5*max_width + max_left - left[[ii]],
                          just="left", width=widths[[ii]]))
    grid.draw(gl[[ii]])
    upViewport(2)
  }
  upViewport()
}

grid.newpage()
align_plots(p1, p2)