How To Use The lines() Function In R

The lines() function in R can add one or more straight lines to a plot. Keep reading to learn how to use it.

lines() Function In R

What this function does is take the coordinates you provide and join the corresponding points with lines. This can be useful for adding a line or lines to an existing plot to show a trend or relationship.

You can simply provide two vectors that contain the coordinates of points you want to join as the only arguments. Here’s an example of how to use lines():

# create data points
x = 1:20
y = x ^ 3
plot(x, y)
lines(x, y)

Note: follow this guide if you want to add comments to R code.

In this example, we generate some data and create a new plot using the plot() function. Then, we use the lines() function to add a line to the plot. The lines() function takes the same arguments as the plot() function, so you can specify the x and y values to use for the line.

It is worth noting that you must create a plot with plot() first before calling lines(). Otherwise, it will just refuse to work.

When the x and y components are provided separately like above, they should have the same length. In addition to vectors, you can also use a time series or a two-column matrix.

lines() won’t produce errors when there are NA values in your coordinate data. It will just omit those points and won’t draw any lines connected to them.

You can also add multiple lines to a plot by calling the lines() function multiple times with different x and y values. For example:

x = -10:10
y1 = x ^ 2
y2 = x ^ 3
plot(x, y1)
lines(x, y1)
lines(x, y2)

In this example, we generate two sets of y values and create a new plot using the first set. After that, we use the lines() function twice to add both sets of y values to the plot as separate lines.

You can also customize the appearance of the lines using additional arguments to the lines() function.

For starters, you can use any valid values for the type argument in plot.default here. The example below use ‘b’, meaning both lines and points:

x = -10:10
y = x ^ 3
plot(x, y)
lines(x, y, type = 'b')

The lines() function also recognizes other graphical parameters such as lty, col, and lwd arguments, which can be used to specify the line type, color, and thickness of the lines, respectively.

The lyt argument can be set to integer values: 0 for blank, 1 for solid lines (which is also the default value), 2 for dash lines, 3 for dotted lines, 4 for dot dashes, 5 for long dashes, and 6 for two dashes. On top of that, you can also assign it to character strings (blank, solid, dashed, dotted, dotdash, longdash, or two dash).

Here is how the above line is drawn with dot dashes:

x = -10:10
y = x ^ 3
plot(x, y)
lines(x, y, lty = 4)

Summary

You can use the lines() function in R to add line segments to your plots. The most important data it needs is the coordinates of points you want to join, but you can use other arguments to adjust its line types and other characteristics.