How to Add Points to an Existing Plot in R

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You can use the points() function to add points to an existing plot in R.

This function uses the following basic syntax:

points(df2$x, df2$y, col='red')

This particular syntax adds red points to an existing scatter plot in R using the variables called x and y from a data frame called df2.

The following example shows how to use this syntax in practice.

Example: Add Points to an Existing Plot in R

Suppose we use the plot() function to create the following scatter plot in R:

#create data frame
df1 frame(x=c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10),
                  y=c(4, 5, 5, 4, 6, 8, 12, 15, 19, 22)) 

#create scatterplot
plot(df1$x, df1$y, col='blue', pch=16)

Note: The col argument specifies the color of the points in the plot and the pch argument specifies the symbol to use. A value of 16 represents a filled-in circle.

Now suppose that we would like to add points from another data frame to the plot.

We can use the points() function to do so:

#create second data frame
df2 frame(x=c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10),
                  y=c(14, 12, 9, 9, 8, 5, 4, 5, 3, 2)) 

#add points from df2 to the existing scatter plot
points(df2$x, df2$y, col='red', pch=16)

Notice that the points from the second data frame have been added to the existing plot and are represented by a red color.

If we’d like, we can also use the legend() function to add a legend to the plot so that we can distinguish which points came from which data frame:

#add legend to plot
legend(x=1, y=22, legend=c('df1', 'df2'), fill=c('blue', 'red'))

Note: You can use the points() function as many times as you’d like to add points from as many data frames as you’d like to an existing plot.

Additional Resources

The following tutorials explain how to perform other common tasks in R:

How to Label Points on a Scatterplot in R
How to Add Text Outside of a Plot in R
How to Create a Scatterplot with a Regression Line in R