two-way density plot combined with one way density plot with selected regions in r

Question

# data 
set.seed (123)
xvar <- c(rnorm (1000, 50, 30), rnorm (1000, 40, 10), rnorm (1000, 70, 10))
yvar <-   xvar + rnorm (length (xvar), 0, 20)
myd <- data         


        

Answer 1

Building on Seth's answer (thank you Seth, and you deserve all credits), I improved some of issues raised by the questioner. As comments is too short to answer all issues I choose to use this as answer itself. A couple of issues are still there, need your help:

# data
set.seed (123)
xvar <- c(rnorm (1000, 50, 30), rnorm (1000, 40, 10), rnorm (1000, 70, 10))
yvar <-   xvar + rnorm (length (xvar), 0, 20)
myd <- data.frame (xvar, yvar)

require(ggplot2)

# density plot for xvar
upperp = 80   # upper cutoff
lowerp = 30

middle figure

 g=ggplot(myd,aes(x=xvar,y=yvar))+
    stat_density2d(aes(fill=..level..), geom="polygon") +
    scale_fill_gradient(low="blue", high="green") + 
  scale_x_continuous(limits = c(0, 110)) + 
   scale_y_continuous(limits = c(0, 110)) + theme_bw()

geom_rect two regions

gbig=g+ geom_rect(data=myd, aes(  NULL,  NULL, xmin=0,  
xmax=lowerp,ymin=0, ymax=20), fill='red', alpha=.0051,inherit.aes=F)+ 
geom_rect(aes(NULL,  NULL,   xmin=upperp,            xmax=110, 
 ymin=upperp,            ymax=110),            fill='green',            
  alpha=.0051,
            inherit.aes=F)+   
  opts(legend.position = "none", 
  plot.margin = unit(rep(0, 4), "lines"))

Top histogram with shaded region

    x.dens <- density(myd$xvar)
    df.dens <- data.frame(x = x.dens$x, y = x.dens$y)

   dens_top <- ggplot()+geom_density(aes(myd$xvar, y = ..density..))
+ scale_x_continuous(limits = c(0, 110)) +
geom_area(data = subset(df.dens, x <= lowerp), aes(x=x,y=y), fill = 'red') 
 +  geom_area(data = subset(df.dens, x >= upperp), aes(x=x,y=y), fill = 'green') 
 +    opts (axis.text.x=theme_blank(), axis.title.x=theme_blank(), 
  plot.margin = unit(rep(0, 4), "lines")) + xlab ("") + ylab ("") +  theme_bw()

right histogram with shaded region

   y.dens <- density(myd$yvar)
    df.dens.y <- data.frame(x = y.dens$x, y = y.dens$y)

    dens_right <- ggplot()+geom_density(aes(myd$yvar, y = ..density..))
   + scale_x_continuous(limits = c(0, 110)) +
  geom_area(data = subset(df.dens.y, x <= lowerp), aes(x=x,y=y), 
  fill = 'red') 
  +  geom_area(data = subset(df.dens.y, x >= upperp), aes(x=x,y=y), 
  fill = 'green')
    +      coord_flip() + 


opts (axis.text.x=theme_blank(), axis.title.x=theme_blank(), 
   plot.margin = unit(rep(0, 4), "lines")) + xlab ("") + ylab ("") 
   +  theme_bw()

Make an empty graph to fill in the corner

       empty <- ggplot()+geom_point(aes(1,1), colour="white")+ 
       scale_x_continuous(breaks = NA) + scale_y_continuous(breaks = NA) +
              opts(axis.ticks=theme_blank(),
                   panel.background=theme_blank(),
                   axis.text.x=theme_blank(),
                   axis.text.y=theme_blank(),
                   axis.title.x=theme_blank(),
                   axis.title.y=theme_blank())

Then use the grid.arrange function:

library(gridExtra)
 grid.arrange(dens_top, empty , gbig, dens_right, ncol=2,nrow=2,
 widths=c(2, 1), heights=c(1, 2))

PS: (1) Can somebody help to align the graphs perfectly ? (2) Can someone help to remove the additional space between plots, I tried adjust margins - but there is space between x and y density plot and central plot.

Answer 2

Here is the example for combining multiple plots with alignment:

library(ggplot2)
library(grid)

set.seed (123)
xvar <- c(rnorm (100, 50, 30), rnorm (100, 40, 10), rnorm (100, 70, 10))
yvar <-   xvar + rnorm (length (xvar), 0, 20)
myd <- data.frame (xvar, yvar)

p1 <- ggplot(myd,aes(x=xvar,y=yvar))+
  stat_density2d(aes(fill=..level..), geom="polygon") +
  coord_cartesian(c(0, 150), c(0, 150)) +
  opts(legend.position = "none")

p2 <- ggplot(myd, aes(x = xvar)) + stat_density() +
  coord_cartesian(c(0, 150))
p3 <- ggplot(myd, aes(x = yvar)) + stat_density() + 
  coord_flip(c(0, 150))

gt <- ggplot_gtable(ggplot_build(p1))
gt2 <- ggplot_gtable(ggplot_build(p2))
gt3 <- ggplot_gtable(ggplot_build(p3))

gt1 <- ggplot2:::gtable_add_cols(gt, unit(0.3, "null"), pos = -1)
gt1 <- ggplot2:::gtable_add_rows(gt1, unit(0.3, "null"), pos = 0)

gt1 <- ggplot2:::gtable_add_grob(gt1, gt2$grobs[[which(gt2$layout$name == "panel")]],
                                  1, 4, 1, 4)
gt1 <- ggplot2:::gtable_add_grob(gt1, gt2$grobs[[which(gt2$layout$name == "axis-l")]],
                                 1, 3, 1, 3, clip = "off")

gt1 <- ggplot2:::gtable_add_grob(gt1, gt3$grobs[[which(gt3$layout$name == "panel")]],
                                 4, 6, 4, 6)
gt1 <- ggplot2:::gtable_add_grob(gt1, gt3$grobs[[which(gt3$layout$name == "axis-b")]],
                                 5, 6, 5, 6, clip = "off")
grid.newpage()
grid.draw(gt1)

note that this works with gglot2 0.9.1, and in the future release you may do it more easily.

And finally

you can do that by:

library(ggplot2)
library(grid)

set.seed (123)
xvar <- c(rnorm (100, 50, 30), rnorm (100, 40, 10), rnorm (100, 70, 10))
yvar <-   xvar + rnorm (length (xvar), 0, 20)
myd <- data.frame (xvar, yvar)

p1 <- ggplot(myd,aes(x=xvar,y=yvar))+
  stat_density2d(aes(fill=..level..), geom="polygon") +
  geom_polygon(aes(x, y), 
               data.frame(x = c(-Inf, -Inf, 30, 30), y = c(-Inf, 30, 30, -Inf)),
               alpha = 0.5, colour = NA, fill = "red") +
  geom_polygon(aes(x, y), 
               data.frame(x = c(Inf, Inf, 80, 80), y = c(Inf, 80, 80, Inf)),
               alpha = 0.5, colour = NA, fill = "green") +
  coord_cartesian(c(0, 120), c(0, 120)) +
  opts(legend.position = "none")

xd <- data.frame(density(myd$xvar)[c("x", "y")])
p2 <- ggplot(xd, aes(x, y)) + 
  geom_area(data = subset(xd, x < 30), fill = "red") +
  geom_area(data = subset(xd, x > 80), fill = "green") +
  geom_line() +
  coord_cartesian(c(0, 120))

yd <- data.frame(density(myd$yvar)[c("x", "y")])
p3 <- ggplot(yd, aes(x, y)) + 
  geom_area(data = subset(yd, x < 30), fill = "red") +
  geom_area(data = subset(yd, x > 80), fill = "green") +
  geom_line() +
  coord_flip(c(0, 120))

gt <- ggplot_gtable(ggplot_build(p1))
gt2 <- ggplot_gtable(ggplot_build(p2))
gt3 <- ggplot_gtable(ggplot_build(p3))

gt1 <- ggplot2:::gtable_add_cols(gt, unit(0.3, "null"), pos = -1)
gt1 <- ggplot2:::gtable_add_rows(gt1, unit(0.3, "null"), pos = 0)

gt1 <- ggplot2:::gtable_add_grob(gt1, gt2$grobs[[which(gt2$layout$name == "panel")]],
                                  1, 4, 1, 4)
gt1 <- ggplot2:::gtable_add_grob(gt1, gt2$grobs[[which(gt2$layout$name == "axis-l")]],
                                 1, 3, 1, 3, clip = "off")

gt1 <- ggplot2:::gtable_add_grob(gt1, gt3$grobs[[which(gt3$layout$name == "panel")]],
                                 4, 6, 4, 6)
gt1 <- ggplot2:::gtable_add_grob(gt1, gt3$grobs[[which(gt3$layout$name == "axis-b")]],
                                 5, 6, 5, 6, clip = "off")
grid.newpage()
grid.draw(gt1)

Answer 3

As in the example I linked to above you need the gridExtra package. This is the g you gave.

g=ggplot(myd,aes(x=xvar,y=yvar))+
    stat_density2d(aes(fill=..level..), geom="polygon") +
    scale_fill_gradient(low="blue", high="green") + theme_bw()

use geom_rect to draw the two regions

gbig=g+geom_rect(data=myd,
        aes(  NULL,
            NULL,
            xmin=0,
            xmax=lowerp,
            ymin=-10,
            ymax=20),
        fill='red',
        alpha=.0051,
        inherit.aes=F)+
  geom_rect(aes(    NULL,
            NULL,
            xmin=upperp,
            xmax=100,
            ymin=upperp,
            ymax=130),
            fill='green',
            alpha=.0051,
            inherit.aes=F)+
  opts(legend.position = "none") 

This is a simple ggplot histogram; it lacks your colored regions, but they are pretty easy

  dens_top <- ggplot()+geom_density(aes(x))
  dens_right <- ggplot()+geom_density(aes(x))+coord_flip()

Make an empty graph to fill in the corner

  empty <- ggplot()+geom_point(aes(1,1), colour="white")+
              opts(axis.ticks=theme_blank(), 
                   panel.background=theme_blank(), 
                   axis.text.x=theme_blank(), 
                   axis.text.y=theme_blank(),           
                   axis.title.x=theme_blank(), 
                   axis.title.y=theme_blank())

Then use the grid.arrange function:

library(gridExtra)

grid.arrange(dens_top,     empty     , 
             gbig,         dens_right, 
                 ncol=2, 
                 nrow=2, 
                 widths=c(4, 1), 
                 heights=c(1, 4))

Not very pretty but the idea is there. You will have to make sure the scales match too!