scatterplot
Scatterplot
A scatter plot is a useful way to visualize two quantitative variables in a dataset.
We are exploring mtcars dataset for some amazing data visualization.
We check mtcars dataset description by using following code:
?mtcars
It will open mtcars dataset description in Help window
We attached mtcars dataset in R. By attaching dataset ,we can use variables directly of mtcars .
attach(mtcars)
?plot
For plot graph between any variables , we use plot() .
plot(wt,mpg)
It will plot between mpg and wt in Plots window.
We can add labels associated with axis and color by using this code :
plot(wt,mpg,col=”red”,ylab=”Miles/(US) gallon”,xlab=”Weight (1000 lbs)”)
We add label in x-axis by using xlab parameter and label in y-axis by using ylab parameter.
We can add naming of graph by using main parameter .
plot(wt,mpg,col=”red”,ylab=”Miles/(US) gallon”,xlab=”Weight (1000 lbs)”,main =”Miles per Gallon and Weight”)
hist()
It is used to plot histogram . It is an estimate of the probability distribution of a continuous variable.
hist(mpg,col=”red”)
It shows red frequency bars of mpg variable.
We add breaks parameter , it is used to break the x-axis in given number of breaks.
hist(mpg,col=”red”,breaks = 10)
We assign freq parameter to FALSE to draw lines in density plot.
We can also density plot by using this code:
hist(mpg,col=”red”,freq = FALSE)
lines(density(mpg))
We are using ggplot2 package for more advanced visualization.
We install ggplot2 package :
install.packages(“ggplot2”)
We load ggplot2 package as:
library(ggplot2)
We are using qplot to plot graphs.
?qplot
We determine dimensions of mtcars. It contains 32 rows and 11 columns.
dim(mtcars)
We can see top 6 observations of mtcars dataset
head(mtcars)
We are using qplot() function to plot scatter plot between mpg and wt .
qplot(mpg, wt, data = mtcars)
We have cyl variable which shows number of cylinders. We add colors by cyl values as:
qplot(mpg, wt, data = mtcars, col= cyl)
We change cyl to factor . So , color select values on the basis of cyl value.
qplot(mpg, wt, data = mtcars, colour = factor(cyl))
We add size and shape according to cyl values .
qplot(mpg, wt, data = mtcars,shape=factor(cyl), size = factor(cyl), colour = factor(cyl))
We added two variables by using facets parameter. It is used to add formula to add variables.
qplot(mpg, wt, data = mtcars, facets = vs ~ am)
Similarly , we add formula in facets parameter to represent am and cyl variables.
qplot(mpg, wt, data = mtcars, facets = am ~ cyl)
qplot(mpg,wt,data=mtcars,facets=cyl~.,colour=factor(cyl))
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