Stata 15 help for twoway area

[G-2] graph twoway area -- Twoway line plot with area shading

Syntax

twoway area yvar xvar [if] [in] [, options]

options Description ------------------------------------------------------------------------- vertical vertical area plot; the default horizontal horizontal area plot cmissing(y|n) missing values do not force gaps in area; default is cmissing(y) base(#) value to drop to; default is 0 nodropbase programmer's option sort sort by xvar; recommended

area_options change look of shaded areas

axis_choice_options associate plot with alternative axis

twoway_options titles, legends, axes, added lines and text, by, regions, name, aspect ratio, etc. ------------------------------------------------------------------------- Option base() is rightmost; vertical, horizontal, nodropbase, and sort are unique; see repeated options.

Menu

Graphics > Twoway graph (scatter, line, etc.)

Description

twoway area displays (y,x) connected by straight lines and shaded underneath.

Options

vertical and horizontal specify either a vertical or a horizontal area plot. vertical is the default. If horizontal is specified, the values recorded in yvar are treated as x values, and the values recorded in xvar are treated as y values. That is, to make horizontal plots, do not switch the order of the two variables specified.

In the vertical case, shading at each xvar value extends up or down from 0 according to the corresponding yvar values. If 0 is not in the range of the y axis, shading extends up or down to the x axis.

In the horizontal case, shading at each xvar value extends left or right from 0 according to the corresponding yvar values. If 0 is not in the range of the x axis, shading extends left or right to the y axis.

cmissing(y|n) specifies whether missing values are to be ignored when drawing the area or if they are to create breaks in the area. The default is cmissing(y), meaning that they are ignored. Consider the following data:

+-------------+ | y1 y2 x | |-------------| 1. | 1 2 1 | 2. | 3 5 2 | 3. | 5 4 3 | 4. | . . . | 5. | 6 7 5 | |-------------| 6. | 11 12 8 | +-------------+

Say that you graph these data by using twoway area y1 y2 x. Do you want a break in the area between 3 and 5? If so, you type

. twoway area y1 y2 x, cmissing(n)

and two areas will be drawn, one for the observations before the missing values at observation 4 and one for the observations after the missing values.

If you omit the option (or type cmissing(y)), the data are treated as if they contained

+-------------+ | y1 y2 x | |-------------| 1. | 1 2 1 | 2. | 3 5 2 | 3. | 5 4 3 | 4. | 6 7 5 | 5. | 11 12 8 | +-------------+

meaning that one contiguous area will be drawn over the range (1,8).

base(#) specifies the value from which the shading should extend. The default is base(0), and in the above description of options vertical and horizontal, this default was assumed.

nodropbase is a programmer's option and is an alternative to base(). It specifies that rather than the enclosed area dropping to base(#) -- or base(0) -- it drops to the line formed by (y_1,x_1) and (y_N,x_N), where (y_1,x_1) are the y and x values in the first observation being plotted and (y_N,x_N) are the values in the last observation being plotted.

sort specifies that the data be sorted by xvar before plotting.

area_options set the look of the shaded areas. The most important of these options is color(colorstyle), which specifies the color and opacity of both the area and its outline; see [G-4] colorstyle for a list of color choices. See [G-3] area_options for information on the other area_options.

axis_choice_options associate the plot with a particular y or x axis on the graph; see [G-3] axis_choice_options.

twoway_options are a set of common options supported by all twoway graphs. These options allow you to title graphs, name graphs, control axes and legends, add lines and text, set aspect ratios, create graphs over by() groups, and change some advanced settings. See [G-3] twoway_options.

Remarks

Remarks are presented under the following headings:

Typical use Advanced use Cautions

Typical use

We have quarterly data recording the U.S. GNP in constant 1996 dollars:

. sysuse gnp96

. list in 1/5 +-----------------+ | date gnp96 | |-----------------| 1. | 1967q1 3631.6 | 2. | 1967q2 3644.5 | 3. | 1967q3 3672 | 4. | 1967q4 3703.1 | 5. | 1968q1 3757.5 | +-----------------+

In our opinion, the area under a curve should be shaded only if the area is meaningful:

. sysuse gnp96, clear

. twoway area d.gnp96 date (click to run)

Advanced use

Here is the same graph, but greatly improved with some advanced options:

. twoway area d.gnp96 date, xlabel(36(8)164, angle(90)) ylabel(-100(50)200, angle(0)) ytitle("Billions of 1996 Dollars") xtitle("") subtitle("Change in U.S. GNP", position(11)) note("Source: U.S. Department of Commerce, Bureau of Economic Analysis") (click to run)

Cautions

Be sure that the data are in the order of xvar, or specify area's sort option. If you do neither, you will get something that looks like modern art:

. sysuse gnp96, clear

. generate d = d.gnp96

. generate u = runiform()

. sort u (put in random order)

. twoway area d date (click to run)


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