R: Quantile-Quantile Plots

qqPlot {QTLRel} | R Documentation

## Quantile-Quantile Plots

### Description

Quantile-Quantile Plots With the Ability to Draw Confidence Bands.

### Usage

    qqPlot(y, x = "norm", ...,
       type = "p", xlim = NULL, ylim = NULL,
       xlab = if(is.numeric(x)) deparse(substitute(x)) else x,
       ylab = deparse(substitute(y)),main="Q-Q Plot",
       col = 1, lty = 2, lwd = 1, pch = 1, cex = 0.7, plot.it = TRUE,
       confidence = .95, qqline = c("observed","expected","none"),
       add = FALSE)

### Arguments

`y` | A numeric vector of data values.
`x` | Either a numeric vector of data values, or a character string naming a distribution function such as "norm".
`...` | Parameters passed to the distribution specified by `x` (if non-numerical).
`type` | 1-character string giving the type of plot desired.
`xlim` | The x limits.
`ylim` | The y limits.
`xlab` | A label for the x axis.
`ylab` | A label for the y axis.
`main` | A main title for the plot.
`col` | Color for points and lines.
`lty` | Line type.
`lwd` | Line width.
`pch` | Plotting character for points.
`cex` | Factor for expanding the size of plotted symbols.
`plot.it` | Whether or not to draw a plot. if plotting, points outside the confidence bands will be indicated by different a color.
`confidence` | Confidence level for the confidence band, or `FALSE` for no band.
`qqline` | Whether or not to draw a reference line. if "observed", the line passes through the first and third observed quartiles; if "expected", the point (x,y) is expected to fall on the line if x and y follow the same distribution; if "none", no reference line is drawn.
`add` | Add to an existing plot if true.

### Details

If `x` is numeric, a two-sample test of the null hypothesis that `x` and `y` were drawn from the same continuous distribution is performed. Alternatively, `x` can be a character string naming a continuous distribution function. In such a case, a one-sample test is carried out of the null that `y` was draw from distribution `x` with parameters specified by "...".

### Value

`x` | Quantiles of `x`
`y` | Quantiles of `y`
`lower, upper` | Lower and upper limits if `confidence` is specified

### References

George Marsaglia, Wai Wan Tsang and Jingbo Wang (2003), Evaluating Kolmogorov's distribution. Journal of Statistical Software 8 (18): 1-4.

Vijayan N. Nair (1982). Q-Q plots with confidence bands for comparing several populations.

William J. Conover (1971). Practical Nonparametric Statistics. New York: John Wiley & Sons.

### See Also

`ks.test`.

### Examples

    ## Not run:
    par(mfrow=c(1,2))
    x<- rnorm(200, mean=0.7,sd=2); y<- rnorm(200, sd=2)
    qqPlot(y,x,qqline="exp")
    qqPlot(y=y,x="norm",sd=2)
    ks.test(x,y)

    ## End(Not run)

[Package QTLRel version 1.0 Index]