ggplot2: Grammar

head(mpg)

## [1] 18 15 18 16 17 15

qplot(displ, hwy, data = mpg, colour = factor(cyl))

## Error: ggplot2 doesn't know how to deal with data of class numeric

qplot(displ, hwy, data=mpg, colour=factor(cyl), geom="line")

## Error: ggplot2 doesn't know how to deal with data of class numeric

qplot(displ, hwy, data=mpg, colour=factor(cyl), geom="bar", 
  stat="identity", position = "identity")

## Error: ggplot2 doesn't know how to deal with data of class numeric

# A complex plot without name
qplot(displ, hwy, data=mpg, colour=factor(cyl)) + 
  geom_smooth(data = subset(mpg, cyl != 5), method="lm")

## Error: ggplot2 doesn't know how to deal with data of class numeric

# A more complex plot with facets and multiple layers.
qplot(displ, hwy, data=mpg, facets = . ~ year) + geom_smooth()

## Error: ggplot2 doesn't know how to deal with data of class numeric

x <- 1:10
y <- factor(letters[1:5])
qplot(x, x, size = x)

qplot(x, x, 1:10, colour = x)

qplot(y, y, 1:10, shape = y)

qplot(y, y, 1:10, colour = y)

x1 <- c(1,10)
y1 <- c(1, 5)
p <- qplot(x1, y1, geom="blank", xlab=NULL, ylab=NULL) + theme_bw()
p 

p + coord_trans(y="log10")

p + coord_polar()

p <- qplot(displ, hwy, data = mpg, colour = factor(cyl))

## Error: ggplot2 doesn't know how to deal with data of class numeric

summary(p)

## data: [0x0]
## mapping:  x = x1, y = y1
## faceting: facet_null() 
## -----------------------------------
## geom_blank:  
## stat_identity:  
## position_identity: (width = NULL, height = NULL)

# Save plot object to disk
# save(p, file = "plot.rdata")
# Load from disk
# load("plot.rdata")
# Save png to disk
# ggsave("plot.png", width = 5, height = 5)