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help for qfrplot
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Quantile plots of fitted and residuals

qfrplot [plottype] [, super [normal|gaussian] combine(graph_options)
fplot(qplot_options) rplot(qplot_options) graph_options]

Description

qfrplot plots quantile plots of fitted values, minus their mean, and
residuals from the previous estimation command. Fitted values are
whatever predict produces by default and residuals are whatever predict,
res produces. Comparing the distributions gives an overview of their
variability and some idea of their fine structure. By default plots are
side-by-side.

The plot type may be one of eight twoway types, namely, area, bar,
connected, dot, dropline, line, scatter or spike. scatter is the default.

The plot is restricted to the estimation sample.

qplot (SJ 4(1) 2004) must be installed.

Remarks

A quantile plot shows ordered values versus the so-called plotting
positions, or if the normal or gaussian option is specified, the
corresponding quantiles of a standard normal (Gaussian) distribution.
For n values ordered minimum first, the plotting positions are
(i - a) / (n - 2a + 1) for i = 1, ..., n, where a is by default 0.5.

W.S. Cleveland in Visualizing data (Hobart Press, Summit, NJ, 1993) gives
many side-by-side quantile plots of fit and residuals, which he calls
"residual-fit spread plots". See example on p.41. However, he also uses
this term for side-by-side time series plots of fit and residuals. See
example on p.157. The command name and description here emphasise the use
of a quantile plot.

Options

super specifies that plots are to be superimposed, not side-by-side. If
super is specified, use combine() to control other characteristics of
the combined plot.

normal specifies that standard normal quantiles should be shown instead
of plotting positions. gaussian is an exact synonym except that by
default the text Gaussian will appear within the axis title, rather
than normal.

fplot() specifies options of qplot controlling the quantile plot of
fitted values. fplot() is irrelevant if super is also specified.

rplot() specifies options of qplot controlling the quantile plot of
residuals. rplot() is irrelevant if super is also specified.

combine() specifies options of qplot controlling the quantile plot of
fitted and residuals, whenever super is also specified; and options
of graph combine otherwise.

graph_options are other graph options affecting the combined graph.

Examples

. use auto
. regress mpg weight
. qfrplot

. glm mpg weight, link(power -1)
. qfrplot, norm fplot(yla(,ang(h)))

Author

Nicholas J. Cox, University of Durham, U.K.
n.j.cox@durham.ac.uk

Also see

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