Quantile-Quantile Plots for various distributions
qqPlot creates a QQ plot of the values in x including a line which passes through the first and third quartiles.
qqPlot(x, y, confbounds = TRUE, alpha, main, xlab, ylab, xlim, ylim, border = "red", bounds.col = "black", bounds.lty = 1, start, ...)
- the sample for qqPlot
character string specifying the distribution of x. The function
qqPlotwill support the following character strings for
- negative binomial
distributionis set to normal.
- boolean value: TRUE if confidence bounds should be drawn (default value).
- significance level for the confidence bounds, set on 0.05 by default.
an overall title for the plot: see
a title for the x axis:
a title for the y axis:
- vector giving the range of the x-axis.
- vector giving the range of the y-axis.
numerical value or single character string giving the color of interpolation line.
borderis set to red.
- numerical value or single character string giving the color of confidence bounds lines. By default bounds is set to black.
- numerical value giving the color of confidence bounds lines. By default bounds is set to 1.
- A named list giving the parameters to be fitted with initial values. Must be supplied for some distribution: (see Details).
further graphical parameters: (see
Distribution fitting is deligated to function
fitdistr of the R-package MASS.
For computation of the confidence bounds the variance of the quantiles is estimated using the delta method,
which implies estimation of observed Fisher Information matrix as well as the gradient of the CDF of the fitted distribution.
Where possible, those values are replaced by their normal approximation.
a list containing the x and y quantiles
- sample quantiles
- theoretical quantiles
#set up the plotting window for 6 plots par(mfrow = c(3,2)) #generate random data from weibull distribution x = rweibull(20, 8, 2) #Quantile-Quantile Plot for different distributions qqPlot(x, "log-normal") qqPlot(x, "normal") qqPlot(x, "exponential", DB = TRUE) qqPlot(x, "cauchy") qqPlot(x, "weibull") qqPlot(x, "logistic")