Graphics Reference
In-Depth Information
The reason for this is that the marker has a
line
color and a
fill
color, and by default,
they are the same color, so it is impossible to see the effect of changing the thickness of the
line around the marker. However, if we make the
line
and
fill
colors different, as in the
following example, we can see the effect of the
mlwidth()
option:
. twoway scatter propval100 rent700, mlwidth(thick)
mlcolor(black) mfcolor(gs13)
Options when using by()
Using the
by()
option changes the meaning of some options. Consider the following
example:
. twoway scatter propval100 rent700, by(north) title(My title)
We might think that the
title()
option will provide an overall title for the graph, as it
would when the
by()
option is not included. However, actually, each graph will have “My
title” as the title; the graph as a whole will not. Instead, to provide an overall title for the
graph, we would specify the command this way:
. twoway scatter propval100 rent700, by(north, title(My title))
When using the
legend()
option combined with the
by()
option, we should place
options that affect the position of the legend within the
by()
option. Consider this example:
. twoway scatter propval100 popden rent700,
by(north, legend(pos(12))) legend(cols(1))
Here, the
legend(pos(12))
option controls the position of the legend, placing it at
the 12 o'clock position, so we place it within the
by()
option. On the other hand, the
legend(cols(1))
option does not affect the position of the legend, so we place it outside
of the
by()
option. For more details on this, see
Options : By
(272).
Altering the wrong axis
When we use multiple
x
-or
y
-axes, it is easy to modify the wrong axis. Consider this
example:
. twoway (scatter propval100 ownhome)
(scatter rent700 ownhome, yaxis(2)
ytitle(Rents over 700)
)
We might think that the
ytitle()
option will change the title for the second
-axis,
but it will actually change the first axis. Because
ytitle()
is an option that concerns the
overall graph, we should place it at the very end of the graph command, as shown below.
y
. twoway (scatter propval100 ownhome)
(scatter rent700 ownhome, yaxis(2)),
ytitle(Rents over 700, axis(2))
Note that we use the
axis(2)
option to indicate that
ytitle()
should be modified for the
second
y
-axis.
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