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# DXDENSITY procedure

Produces one-dimensional density (or violin) plots (D. B. Baird).

### Options

`BANDWIDTH` = scalar Bandwidth for kernel smoothing (0-1); default density is chosen according to the number of observations The size of the gap (0-1) between envelopes when there are several densities; default 0.1 Transformed scale for the data (`identity`, `log`, `log10`, `logit`, `probit`, `cloglog`, `square`, `exp`, `exp10`, `ilogit`, `iprobit`, `icloglog`, `root`); default is to use the transform defined for `XAXIS` The title for the data axis; default is the name of the `DATA` variate The title for the groups or variates axis; default is to use the name of the `GROUPS` factor Window number for the graph; default 3 Orientation of plots (`horizontal`, `vertical`); default `vert` Method for plotting the density envelope (`fill`, `line`); default `fill` Whether to clear screen before the plot (`clear`, `keep`, `resize`); default `clea`

### Parameters

`DATA` = variates or pointers The data whose density is to be plotted Factor to divide values of a single variate into groups; default `*` i.e. none Title for graph; default uses the names of the data variates and type of plot

### Description

`DXDENSITY` produces density (or violin) plots, using high-resolution graphics. The data are specified by the `DATA` parameter. For a single density plot, `DATA` should be set to a variate. To plot several densities, you can set `DATA` to a pointer of variates. Alternatively, it can be set to a single variate, with the `GROUPS` parameter then specifying a factor to identify groups of points whose densities are to be plotted separately.

The points are plotted along a line, with a kernel density smooth on either side to indicate the density of points along the line. The `BANDWIDTH` option specifies the band width for the kernel smoothing; larger values make it smoother, and smaller values allow it to be rougher. The default is chosen automatically, according to the number of observations. The gap between the envelopes for different variates or groups can be defined by the `GAP` option; this must be between 0 and 1 (default 0.1).

The `METHOD` option controls how the density envelope is drawn around the points, either as a filled region or as a line. You can use the `TITLE` parameter to supply an overall title for the plot. The `AXISTITLE` and `GROUPSTITLE` options can be used to supply titles for the data and groups axes respectively. The `WINDOW` option specifies the number of the window to use for the plot (default 3), and the `SCREEN` option controls whether the screen is cleared first, as usual (see `DGRAPH`).

The data can be transformed by using the `TRANSFORM` option. If this is not set, `DXDENSITY` uses the setting of `TRANSFORM`, defined by the `XAXIS` directive for the specified `WINDOW`. The available settings are the same as those of the `TRANSFORM` option of `XAXIS`.

The `ORIENTATION` option controls whether the data axis is horizontal or vertical (default). The `XAXIS` and `YAXIS` directives can be used, prior to using `DXDENSITY`, to set attributes of the axes of the plot in the window that is to be used. Note that, when the orientation is horizontal, the attributes of the x- and y-axes are swapped, so that the x-axis settings are always applied to the data axis.

Options: `BANDWIDTH`, `GAP`, `TRANSFORM`, `AXISTITLE`, `GROUPSTITLE`, `WINDOW`, `ORIENTATION`, `METHOD`, `SCREEN`.

Parameters: `DATA`, `GROUPS`, `TITLE`.

### Action with `RESTRICT`

If any of the variates or factors are restricted, only the units not excluded by the restriction will be plotted.

Directive: `DHISTOGRAM`.

Procedures: `DXYDENSITY`, `DOTHISTOGRAM`, `BOXPLOT`, `KERNELDENSITY`, `RUGPLOT`.

Commands for: Graphics.

### Example

```CAPTION   'DXDENSITY Example',\
!t('1) The three variates America, Asia_Oc & Other contain the',\
'heights of volcanoes in three regions of the world.');\
STYLE=meta,plain
VARIATE   [VALUES=199,197,193,185,177,172,157,156,140,140,130,126,124,124,113,\
102,100,102,94,93,89,86,83,83,83,82,77,73,70,62,58,51,51,42,40,\
34,36,67,67,66,60,57,57,53,49,43,43,40,35,35] America
&         [VALUES=156,137,125,122,120,112,109,103,100,100,96,95,95,90,83,\
81,81,81,77,75,75,73,71,71,67,66,66,64,62,60,60,60,59,58,57,\
56,56,55,54,54,52,52,52,51,50,49,49,48,45,44,44,37,36,36,26,\
26,24,19,11,10,41] Asia_Oc
&         [VALUES=134,125,114,111,100,90,80,75,49,21,21,30,60,17,19] Other
DXDENSITY !P(America,Asia_Oc,Other)
CAPTION   !T('2) The three sets of heights are combined into a single',\
'variate and a factor is set up to specify which values in the',\
'combined variate came from which region.')
VARIATE   [VALUES=#America,#Asia_Oc,#Other] All
FACTOR    [LABELS=!t(America,'Asia/Oceania',Elsewhere);\
VALUES=50(1),61(2),15(3)] Region
DXDENSITY [BANDWIDTH=0.35; AXISTITLE='Height of volcano'; GROUPSTITLE='Region']\
All; GROUP=Region; TITLE='Volcano height by region'
```
Updated on March 8, 2019