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st: RE: xlabels and graph with 2 y-axis
Dr Veit Grote
> I have a simple graph that does not come out as I want to
> (Stata 8.1).
> I have a labeled categorical variable which I would like to
> use as my x-axis, and two numerical variables of different
> scales (2 y-axis). One should be expressed in bars and one
> as a line/connected line (as in the frequency polygon
> example in Statalist just recently).
> 1. First problem: Why is the scale of the bars cut (in my
> data at 30, so that the lower range 0-30 is not displayed)
> whereas the scale of the 2nd y-axis is for the whole range
> of the data? OK, I fixed that with options scale/range.
Not sure what kind of answer you want. It's just the way it's
Evidently one design would ensure that by default all bars in
-twoway bar- start at 0, but that would be awkward.
Put it whimsically: the graph's primary identity is
as a -twoway- graph, and only secondarily is it a -bar-
graph. The rule for -twoway-'s default is _not_ to
insist on starting axes at 0. That's what takes precedence
here. At least, that's my interpretation.
Admittedly, the rule causes puzzles at times. I have been
caught a few times wondering why some of my bars had
disappeared and searched for my bug as an explanation.
This happened when I was developing -eqprhistogram-, which
is really a wrapper for -twoway bar-. After having worked out
what was going on, with an excellent assist
from Vince Wiggins, I wired in -yscale(range(0))- as
> 2. Second problem: I am unable to display the labels of the
> x-axis? What is the trick? One desperate try was:
> twoway bar y1 x || connected y2 x, xlabel(#7, valuelabels) yaxis(2)
I got the value labels to appear when I insisted -legend(off)-.
Can't explain that one at all.
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