qqt {limma} | R Documentation

## Student's t Quantile-Quantile Plot

### Description

Plots the quantiles of a data sample against the theoretical quantiles of a Student's t distribution.

### Usage

    qqt(y, df = Inf, ylim = range(y), main = "Student's t Q-Q Plot",
        xlab = "Theoretical Quantiles", ylab = "Sample Quantiles", plot.it = TRUE, ...)

### Arguments

`y` | a numeric vector or array containing the data sample
`df` | degrees of freedom for the t-distribution. The default `df=Inf` represents the normal distribution.
`ylim` | plotting range for `y`
`main` | main title for the plot
`xlab` | x-axis title for the plot
`ylab` | y-axis title for the plot
`plot.it` | whether or not to produce a plot
`...` | other arguments to be passed to `plot`

### Details

This function is analogous to `qqnorm` for normal probability plots. In fact `qqt(y,df=Inf)` is identical to `qqnorm(y)` in all respects except the default title on the plot.

### Value

A list is invisibly returned containing the values plotted in the QQ-plot:

`x` | theoretical quantiles of the t-distribution
`y` | the data sample, same as input `y`

### Author(s)

Gordon Smyth

### See Also

`qqnorm`

### Examples

    y <- rt(50,df=4)
    qqt(y,df=4)

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