Sample Codes for illustration of ggplot2

## Sample Codes for illustration of ggplot2
## Susheel Shukla 09-01-2017

### install & load ggplot library
install.package("ggplot2")
library("ggplot2")

### show info about the data
head(diamonds)
head(mtcars)



### comparison qplot vs ggplot                                                      

# qplot histogram
qplot(clarity, data=diamonds, fill=cut, geom="bar")                          

# ggplot histogram -> same output
ggplot(diamonds, aes(clarity, fill=cut)) + geom_bar()

P.S. - both qplot and ggplot having same graph (as shown here)

### how to use qplot                                     

# scatterplot

qplot(wt, mpg, data=mtcars)

# transform input data with functions

qplot(log(wt), mpg - 10, data=mtcars)

# add aesthetic mapping (hint: how does mapping work)

qplot(wt, mpg, data=mtcars, color=qsec)

# change size of points (hint: color/colour, hint: set aesthetic/mapping)

qplot(wt, mpg, data=mtcars, color=qsec, size=3)

qplot(wt, mpg, data=mtcars, colour=qsec, size=I(3))  #aesthetics can be set to a constant value instead of mapping

# use alpha blending

qplot(wt, mpg, data=mtcars, alpha=qsec)        # values between 0 (transparent) and 1 (opaque)

# continuous scale vs. discrete scale

head(mtcars)

qplot(wt, mpg, data=mtcars, colour=cyl)

levels(mtcars$cyl)

qplot(wt, mpg, data=mtcars, colour=factor(cyl))

# use different aesthetic mappings

qplot(wt, mpg, data=mtcars, shape=factor(cyl))

qplot(wt, mpg, data=mtcars, size=qsec)

# combine mappings (hint: hollow points, geom-concept, legend combination)

qplot(wt, mpg, data=mtcars, size=qsec, color=factor(carb))

qplot(wt, mpg, data=mtcars, size=qsec, color=factor(carb), shape=I(1))

qplot(wt, mpg, data=mtcars, size=qsec, shape=factor(cyl), geom="point")

qplot(wt, mpg, data=mtcars, size=factor(cyl), geom="point")

# bar-plot

qplot(factor(cyl), data=mtcars, geom="bar")

# flip plot by 90°

qplot(factor(cyl), data=mtcars, geom="bar") + coord_flip() 

# difference between fill/color bars

qplot(factor(cyl), data=mtcars, geom="bar", fill=factor(cyl))

qplot(factor(cyl), data=mtcars, geom="bar", colour=factor(cyl))

                             

# fill by variable

qplot(factor(cyl), data=mtcars, geom="bar", fill=factor(gear))

# use different display of bars (stacked, dodged, identity)

head(diamonds)

qplot(clarity, data=diamonds, geom="bar", fill=cut, position="stack")

qplot(clarity, data=diamonds, geom="bar", fill=cut, position="dodge")

qplot(clarity, data=diamonds, geom="bar", fill=cut, position="fill")

qplot(clarity, data=diamonds, geom="bar", fill=cut, position="identity")

qplot(clarity, data=diamonds, geom="freqpoly", group=cut, colour=cut, position="identity")

qplot(clarity, data=diamonds, geom="freqpoly", group=cut, colour=cut, position="stack")