Produce a Shaded Curve
Sometimes the area under a density curve has to be color shaded, for instance to illustrate a p-value or a specific region under the normal curve.
This function draws a curve corresponding to a function over the interval [from, to]. It can plot also an expression in the variable xname, default x.
Shade(expr, col = par("fg"), breaks, density = 10, n = 101, xname = "x", ...)expr |
the name of a function, or a |
col |
color to fill or shade the shape with. The default is taken from |
breaks |
numeric, a vector giving the breakpoints between the distinct areas to be shaded differently. Should be finite as there are no plots with infinite limits. |
density |
the density of the lines as needed in polygon. |
n |
integer; the number of x values at which to evaluate. Default is 101. |
xname |
character string giving the name to be used for the x axis. |
... |
the dots are passed on to |
Useful for shading the area under a curve as often needed for explaining significance tests.
A list with components x and y of the points that were drawn is returned invisibly.
Andri Signorell <andri@signorell.net>
curve(dt(x, df=5), xlim=c(-6,6),
main=paste("Student t-Distribution Probability Density Function, df = ", 5, ")", sep=""),
type="n", las=1, ylab="probability", xlab="t")
Shade(dt(x, df=5), breaks=c(-6, qt(0.025, df=5), qt(0.975, df=5), 6),
col=c(hred, hblue), density=c(20, 7))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.