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Last data update: 2014.03.03

R: Plot a Normal Curve with Shaded Intervals by Standard...

prob.znorm

R Documentation

Plot a Normal Curve with Shaded Intervals by Standard Deviation

Description

Display a normal curve with shading according to the z-score, the number of standard deviations from the mean.

Usage

prob.znorm(mu=0, sigma=1, color.border="gray10",
         r=.10, g=.34, b=.94, a=.20,
         xlab="", ylab="", main="", 
         y.axis=FALSE, z=TRUE, mag=.9, ...)

Arguments

`mu`	Population mean of normal distribution.
`sigma`	Population standard deviation of normal distribution.
`color.border`	Color of the border of the normal curve.
`r`	Red component of fill color, from 0 to 1.
`g`	Green component of fill color, from 0 to 1.
`b`	Blue component of fill color, from 0 to 1.
`a`	Alpha component of fill color, that is, the transparency, from 0 to 1.
`xlab`	Label for the horizontal axis.
`ylab`	Label for the optional vertical axis.
`main`	Label for the graph title.
`y.axis`	If `TRUE`, then a vertical axis is included.
`z`	If `TRUE`, then include z-values on the horizontal-axis. Set to `FALSE` if `mu=0` and `sigma=1`.
`mag`	Magnification factor for the axis labels, the value of `cex.axis`.
`...`	Other parameter values for graphics.

Details

Provide a normal curve with shading of each interval defined by the number of standard deviations from the mean. The layers are written with transparency, and over-written so that the middle interval is the darkest and the most extreme intervals, beyond three standard deviations from the mean, are the lightest. Specify a=0 to turn off the colors. Higher values of the alpha channel, as specified by a, yield darker colors. Specify a=1 for the same solid color for all intervals.

The normal densities are calculated with dnorm and plotted with plot.

Author(s)

David W. Gerbing (Portland State University; gerbing@pdx.edu)

Examples

# Mu=0, Sigma=1: Standard normal 
prob.znorm()

# distribution for height of American women, mu=65.5, sigma=2.5
prob.znorm(65.5, 2.5, xlab="Height of American Women")

# do a red fill color
prob.znorm(65.5, 2.5, r=.9, xlab="Height of American Women")