16.1 Scatter plots

A scatter plot has points that show the relationship between two sets of data.

• Simple scatter plot

# Create 2 vectors
x <- 1:10
y <- x^2

# Plot x against y
plot(x, y)

Note that if one vector only is given as an input, it will be plotted against the indices of each element

• Add arguments:
  • col: color
  • pch: type of point
  • type: “l” for line, “p” for point, “b” for both point and line
  • main: title of the plot

plot(x, y, 
    col="red", 
    pch=2, 
    type="b", 
    main="a pretty scatter plot")

• You can play a bit:

plot(x, y, 
    col=1:10, 
    pch=1:10, 
    cex=1:10, 
    type="b", 
    main="an even prettier scatter plot")

Different type of points that you can use:

About colors

• Color codes 1 to 8 are taken from the palette() function and respectively code for: “black”, “red”, “green3”, “blue”, “cyan”, “magenta”, “yellow”, “gray”.

# see the 8-color palette:
palette()

• There is a larger set of build-in colors that you can use:

# see all 657 possible build-in colors:
colors()

# looking for blue only? You can pick from 66 blueish options:
grep("blue", colors(), value=TRUE)

You can also find them here.

• change the default palette with one of your choice:

palette(grep("blue", colors(), value=TRUE))

• change the palette back to default

palette("default")