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Quantile-quantile plot

`qqplot(`

displays a
quantile-quantile plot of the quantiles of the sample data
`x`

)`x`

versus the theoretical quantile values from a normal
distribution. If the distribution of `x`

is normal, then the
data plot appears linear.

`qqplot`

plots each data point in
`x`

using plus sign (`'+'`

) markers and
draws two reference lines that represent the theoretical distribution. A solid
reference line connects the first and third quartiles of the data, and a dashed
reference line extends the solid line to the ends of the data.

`qqplot(___,`

displays a quantile-quantile plot with the quantiles specified in the vector
`pvec`

)`pvec`

. Specify `pvec`

after any of
the input argument combinations in the previous syntaxes.

`qqplot(`

uses the
plot axes specified by the `ax`

,___)`Axes`

object `ax`

.
The option `ax`

can precede any of the input argument
combinations in the previous syntaxes.

returns
the handles (`h`

= qqplot(___)`h`

) to the lines in the quantile-quantile
plot.