Add Color Between Two Points of Kernel Density Plot in R Programming – Using with() Function

plot() and with() functions are used to draw and add color between a particular area of two points of Kernel Density Plot in R Language.

Draw a Kernel Density plot

plot() function in R Language is used to draw a Kerner Density Plot

Syntax: plot(dens_x)

Parameters:
dens_x: Default plot of density.

Returns: Kernel density plot

# Create example data

set.seed(72500)
x <- rnorm(800)
dens_x <- density(x)
plot(dens_x)

Output:

Adding Color to Plot

with() function is used to add color between two points of the graph.

Syntax:
with(dens_x,
polygon(x = c(x),
y = c(0, y[x_low:x_high], 0),
col = ” “))

Parameters:
dens_x: Default plot of density.
x_low, x_high: lower limit and upper limit of colored area
col: Name of color

Returns: Color plot between to particular plots with specified color.

# color the plot

set.seed(72500)
x <- rnorm(800)
dens_x <- density(x)
plot(dens_x)
x_low <- min(which(dens_x$x >= - 0.5))   # Define lower limit of colored area
x_high <- max(which(dens_x$x < 1))       # Define upper limit of colored area
with(dens_x,                             # Add color between two limits
     polygon(x = c(x[c(x_low, x_low:x_high, x_high)]),
             y = c(0, y[x_low:x_high], 0),
             col = "darkgreen"))

Output: