In lampk/Lmisc: Miscellaneous functions from LamPK

ggplot2

R cookbook
Advance ggplot:
- ggplot2: cheatsheet: http://zevross.com/blog/2014/08/04/beautiful-plotting-in-r-a-ggplot2-cheatsheet-3/
- Under the hood of ggplot2 graphics in R: http://zevross.com/blog/2014/11/20/under-the-hood-of-ggplot2-graphics-in-r/

## dataset
library(ggplot2)
nmmaps <- read.csv("http://zevross.com/blog/wp-content/uploads/2014/08/chicago-nmmaps.csv", as.is = TRUE)
nmmaps$date <- as.Date(nmmaps$date)
nmmaps <- nmmaps[nmmaps$date>as.Date("1996-12-31"),]
nmmaps$year <- substring(nmmaps$date,1,4)
head(nmmaps)

## under the hood: ggplot_gtable, ggplot_build
## the initial plot
ggplot(nmmaps, aes(date, temp)) + geom_point(color = "chartreuse4") + facet_wrap(~ year, ncol = 2)

## to eliminate the second x-axis
### ggplot_build: outputs a list of data frames (one for each layer) and a panel object with information about axis limits among other things
### ggplot_gtable: get all grid graphical object ("grobs") neccessary for displaying the plot
g <- ggplot(nmmaps, aes(date,temp)) + geom_point(color = "chartreuse4") + facet_wrap(~ year, ncol = 2)
gTable <- ggplot_gtable(ggplot_build(g))

### print each of the grobs to a separate page in a PDF and investigate
library(grid) # we need grid for several functions
pdf(file = file.path("grobs.pdf"))
for(i in 1:length(gTable$grobs)){
  grid.draw(gTable$grobs[[i]])
  grid.text(i, x = unit(0.1, "npc"), y = unit(0.1, "npc"))
  grid.newpage()
}
dev.off()

### tracking down axis label
gTable$grobs[[17]]
attributes(gTable$grobs[[17]])
attributes(gTable$grobs[[17]]$children)
attributes(gTable$grobs[[17]]$children[2])
attributes(gTable$grobs[[17]]$children[2]$axis)
gTable$grobs[[17]]$children[2]$axis$grobs 
attributes(gTable$grobs[[17]]$children[2]$axis$grobs[[2]])
gTable$grobs[[17]]$children[2]$axis$grobs[[2]]$label 

### assigning the empty string instead of the years
gTable$grobs[[17]]$children[2]$axis$grobs[[2]]$label<-""

### plot gTable using grid.draw()
grid.draw(gTable)

### find and get rid of the tick marks
gTable$grobs[[17]]$children[2]$axis$grobs[[1]]$y<-rep(unit(0, units="cm"),5)
grid.draw(gTable)

### to rotate the x-axis on the 3rd plot
#### attributes(gTable$grobs[[16]]$children[2]$axis$grobs[[2]])

#### Change the rotation
gTable$grobs[[16]]$children[2]$axis$grobs[[2]]$rot<-30

#### Rotation make text cramped with text so add x and y space
gTable$grobs[[16]]$children[2]$axis$grobs[[2]]$x<-
  gTable$grobs[[16]]$children[2]$axis$grobs[[2]]$x-unit(0.025, "npc")

gTable$grobs[[16]]$children[2]$axis$grobs[[2]]$y<-
  gTable$grobs[[16]]$children[2]$axis$grobs[[2]]$y-rep(unit(0.1, units="cm"),5)

#### move the x-label left & down
gTable$grobs[[18]]$x<-unit(0.25, units="npc")
gTable$grobs[[18]]$y<-unit(0.1, units="npc")
grid.draw(gTable)