Grid in an R plot

The grid command seems to draw grid lines where-ever it feels like. I usually use abline to put lines exactly where I want them. For example,

abline(v=(seq(0,100,25)), col="lightgray", lty="dotted")
abline(h=(seq(0,100,25)), col="lightgray", lty="dotted")

Good luck!

See help(grid) which works with standard graphics -- short example:

R> set.seed(42)
R> plot(cumsum(rnorm(100)), type='l')
R> grid()

The ggplot2 package defaults to showing grids due to its 'Grammar of Graphics' philosophy. And lattice has a function panel.grid() you can use in custom panel functions.

By the way, there are search functions for help as e.g. help.search("something") and there is an entire package called sos to make R web searches more fruitful.

Another option is using the axis function for vertical and horizontal grid lines:

x <- rnorm(100)
plot(x)
# Vertical grid
axis(1, tck = 1, lty = 2, col = "gray")
# Horizontal grid  
axis(2, tck = 1, lty = 2, col = "gray")

# Only vertical grid
plot(x)
# Vertical grid
axis(1, tck = 1, lty = 2, col = "gray")

# Only horizontal grid
plot(x)
# Horizontal grid  
axis(2, tck = 1, lty = 2, col = "gray")

^{Created on 2022-08-20 with reprex v2.0.2}

You can specify the position of the grid lines using the at argument.