We will use the base graphics for this recipe, so all you need to do is run the recipe at the R prompt. It is good practice to save your code as a script for use again later.

Let's use the city rainfall example again to see how we can add grid lines to that graph:

rain<-read.csv("cityrain.csv")
plot(rain$Tokyo,type="b",lwd=2,
xaxt="n",ylim=c(0,300),col="black",
xlab="Month",ylab="Rainfall (mm)",
main="Monthly Rainfall in Tokyo")
axis(1,at=1:length(rain$Month),labels=rain$Month)

grid()

It's as simple as that! Adding a simple default grid just necessitates calling the grid() function without passing any arguments. The grid() function automatically computes the number of cells in the grid and aligns with the tick marks on the default axes. It uses the abline() function (that we will see again in the next recipe) to draw the grid lines...