R: qq-plot Between Two Vectors of Data with 95 Percent...

qqplot {extRemes} | R Documentation

## qq-plot Between Two Vectors of Data with 95 Percent Confidence Bands

### Description

QQ-plot between two data vectors with 95 percent confidence bands based on the Kolmogorov-Smirnov statistic (Doksum and Sievers, 1976).

### Usage

    qqplot(x, y, pch = 20, xlab = "x Quantiles", ylab = "y Quantiles", regress = TRUE,
        make.plot = TRUE, ...)

    ## S3 method for class 'qqplot'
    plot(x, ...)

    ## S3 method for class 'qqplot'
    summary(object, ...)

### Arguments

`x` | `qqplot`: numeric vector of length 'm' giving one data set. `plot` method function: list object of class “qqplot” returned by `qqplot`.
`object` | list object of class “qqplot” returned by `qqplot`.
`y` | numeric vector of length 'n' giving the other data set.
`pch` | Plot character.
`xlab` | Character string giving the label for the abscissa axis.
`ylab` | Character string giving the label for the ordinate axis.
`regress` | logical, should a regression line be fit to the quantiles?
`make.plot` | logical, should the plot be created (TRUE) or not (FALSE)?
`...` | Other optional arguments to the plot function. Not used by `summary` method function.

### Details

Plots the sorted (missing-values removed) 'x' values against the sorted, and interpolated (via the approxfun function from package stats), 'y' values. Confidence bands are about the sorted and interpolated 'y' values using +/- K/sqrt(M), where

K = 1.36

and

M = m*n / (m+n).

The `plot` method function does exactly the same thing as `qqplot` except that it does not need to do any calculations.

The `summary` method function merely displays the original call to the function unless a regression line was fit between the quantiles, in which case summary information is displayed for the regression (i.e., the `summary` method function for `lm` is run on the “lm” object).

### Value

An object of class “qqplot” is invisibly returned by each function (in the case of the method functions, the object entered is simply returned invisibly). This is a list object with components:

`call` | calling string
`names` | list object with components x and y giving the object names for the objects passed into x and y, resp.
`regression` | If regress was TRUE, then this is the fitted regression object as returned by lm. Otherwise, this component is not included.
`qdata` | data frame with components: x and y giving the quantiles for x and y, resp., and lower and upper giving the lower and upper 95 percent confidence bands, resp.

### Author(s)

Peter Guttorp, peter “at” stat.washington.edu

### References

Doksum, K.A. and G.L. Sievers, 1976. Plotting with confidence: graphical comparisons of two populations. Biometrika, 63 (3), 421–434.

### See Also

`approxfun`, `qqnorm`, `shiftplot`

### Examples

    z <- rnorm(100)
    y <- rexp(100)
    qqplot( z, y)
    qqplot( y, z)

    data( ftcanmax)
    qqplot( ftcanmax[,"Prec"], z)
    obj <- qqplot( ftcanmax[,"Prec"], y, make.plot=FALSE)
    plot(obj)
    summary(obj)

[Package extRemes version 2.0-12 Index]