qqskewlap function

Skew-Laplace Quantile-Quantile and Percent-Percent Plots

qqskewlap produces a skew-Laplace QQ plot of the values in y.

ppskewlap produces a skew-Laplace PP (percent-percent) or probability plot of the values in y.

If line = TRUE, a line with zero intercept and unit slope is added to the plot.

Graphical parameters may be given as arguments to qqskewlap, and ppskewlap.

qqskewlap(y, mu = 0, alpha = 1, beta = 1,
          param = c(mu, alpha, beta),
          main = "Skew-Laplace Q-Q Plot",
          xlab = "Theoretical Quantiles",
          ylab = "Sample Quantiles",
          plot.it = TRUE, line = TRUE, ...)

ppskewlap(y, mu = 0, alpha = 1, beta = 1,
          param = c(mu, alpha, beta),
          main = "Skew-Laplace P-P Plot",
          xlab = "Uniform Quantiles",
          ylab = "Probability-integral-transformed Data",
          plot.it = TRUE, line = TRUE, ...)

Arguments

• y: The data sample.
• mu: The location parameter, set to 0 by default.
• alpha, beta: The shape parameters, both set to 1 by default.
• param: Parameters of the skew-Laplace distribution.
• xlab, ylab, main: Plot labels.
• plot.it: Logical. TRUE denotes the results should be plotted.
• line: Logical. If TRUE, a line with zero intercept and unit slope is added to the plot.
• ...: Further graphical parameters.

Returns

For qqskewlap and ppskewlap, a list with components: - x: The x coordinates of the points that are be plotted.

• y: The y coordinates of the points that are be plotted.

References

Wilk, M. B. and Gnanadesikan, R. (1968) Probability plotting methods for the analysis of data. Biometrika. 55 , 1--17.

See Also

ppoints, dskewlap.

Examples

par(mfrow = c(1, 2))
y <- rskewlap(1000, param = c(2, 0.5, 1))
qqskewlap(y, param = c(2, 0.5, 1), line = FALSE)
abline(0, 1, col = 2)
ppskewlap(y, param = c(2, 0.5, 1))