Preparing Graphs - Agricultural Statistical Data Analysis Using Stata - page 172

computers, these items are available either under the Graph menu or
at the top of the Window (see Figure 9.3).
Finally, on the lower right part of the Graph Editor window on
Macintosh computers are three buttons (Record, Pause, and Play)
that are used to record a sequence of changes to a graph that can be
saved and used later. These icons are available at the top center of the
window on Windows computers (see Figure 9.3). This can be particu-
larly useful if you have several graphs to create that will be similar in
appearance and detail.
Many of the listed graph types under the Graphics menu are par-
ticularly useful for evaluating a dataset to meet certain underlying
criteria like normality. Some of these graphs also can be helpful in
exploring relationships between variables. And, finally, many of the
listed graphs are some of the most frequently used. The Bar chart,
Dot chart, and Pie chart are commonly used and are self-explanatory.
I have illustrated the use of the Bar chart above.
The Histogram item under the Graphics menu constructs a his-
togram or frequency bar graph with the data's frequency within a
category represented by the height of the bar. The number of bars can
be controlled either as continuous where the number of bars or bins
are specified or discrete where each individual value is represented.
Open the dataset Large Onion Dataset 2001-02.dta and enter the
following:
histogram yield, normal
This constructs a histogram of onion yields and superimposes the
normal density function over the histogram. Once this graph has
been constructed it can be edited by selecting the Graph Editor icon
at the top of the window (Figure 9.6).
Select the Graph Editor icon to put the graph in editing mode
and select the Record button in the lower right of the window on a
Macintosh or the same button in the upper center on a Windows com-
puter. Change the color of the bars, add a title, subtitle, change the
background color to white, and change the x -axis label (Figure 9.7).
Once these changes have been made, click the Record button again
to stop recording and save the file. Just such a file was created called
Histogram Defined.grec and can be used over and over again.