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ppPlot: Probability Plots for various distributions

Source: R/1.3_Distr_DistrCollection_Functions.R
ppPlot.Rd

Function ppPlot creates a Probability plot of the values in x including a line.

Usage

ppPlot(
  x,
  distribution,
  confbounds = TRUE,
  alpha,
  probs,
  main,
  xlab,
  ylab,
  xlim,
  ylim,
  border = "red",
  bounds.col = "black",
  bounds.lty = 1,
  start,
  showPlot = TRUE,
  axis.y.right = FALSE,
  bw.theme = FALSE
)

Arguments

x

Numeric vector containing the sample data for the ppPlot.

distribution

Character string specifying the distribution of x. The function ppPlot will support the following character strings for distribution:

  • `beta`

  • `cauchy`

  • `chi-squared`

  • `exponential`

  • `f`

  • `gamma`

  • `geometric`

  • `log-normal`

  • `lognormal`

  • `logistic`

  • `negative binomial`

  • `normal`

  • `Poisson`

  • `weibull`

By default distribution is set to `normal`.

confbounds

Logical value: whether to display confidence bounds. Default is TRUE.

alpha

Numeric value: significance level for confidence bounds, default is `0.05`.

probs

Vector containing the percentages for the y axis. All the values need to be between `0` and `1`. If `probs` is missing it will be calculated internally.

main

Character string: title of the plot.

xlab

Character string: label for the x-axis.

ylab

Character string: label for the y-axis.

xlim

Numeric vector of length 2: limits for the x-axis.

ylim

Numeric vector of length 2: limits for the y-axis.

border

Character or numeric: color for the border of the line through the quantiles. Default is `red`.

bounds.col

Character or numeric: color for the confidence bounds lines. Default is `black`.

bounds.lty

Numeric or character: line type for the confidence bounds lines. This can be specified with either an integer (0-6) or a name:

  • 0: blank

  • 1: solid

  • 2: dashed

  • 3: dotted

  • 4: dotdash

  • 5: longdash

  • 6: twodash

Default is `1` (solid line).

start

A named list giving the parameters to be fitted with initial values. Must be supplied for some distributions (see Details).

showPlot

Logical value indicating whether to display the plot. By default, showPlot is set to TRUE.

axis.y.right

Logical value indicating whether to display the y-axis on the right side. By default, axis.y.right is set to FALSE.

bw.theme

Logical value indicating whether to use a black-and-white theme from the ggplot2 package for the plot. By default, bw.theme is set to FALSE.

Value

The function ppPlot returns an invisible list containing:

x

x coordinates.

y

y coordinates.

int

Intercept.

slope

Slope.

plot

The generated PP plot.

Details

Distribution fitting is performed using the FitDistr function from this package. For the computation of the confidence bounds, the variance of the quantiles is estimated using the delta method, which involves the estimation of the 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.

See also

qqPlot, FitDistr.

Examples

set.seed(123)
ppPlot(rnorm(20, mean=90, sd=5), "normal",alpha=0.30)

ppPlot(rcauchy(100), "cauchy")

ppPlot(rweibull(50, shape = 1, scale = 1), "weibull")

ppPlot(rlogis(50), "logistic")

ppPlot(rlnorm(50) , "log-normal")

ppPlot(rbeta(10, 0.7, 1.5),"beta")

ppPlot(rpois(20,3), "poisson")

ppPlot(rchisq(20, 10),"chi-squared")

ppPlot(rgeom(20, prob = 1/4), "geometric")

ppPlot(rnbinom(n = 20, size = 3, prob = 0.2), "negative binomial")

ppPlot(rf(20, df1 = 10, df2 = 20), "f")