Eric G. Wruck <[email protected]> asks about creating a stacked bar chart
where one of the bars stacks three variables and another bar stacks two other
variables. He then wants these two bars graphed for nine years.
> I have five different variables (call them a, b, c, d, & e) for nine
> years (i.e., 9 obs). I would like to construct a bar chart in the
> following way:
>
> I would like to stack a, b, & c in a single bar, and d & e in
> another & graph them both -over(year)-
>
> I have been able to graph d & e stacked over(year) & I've been able
> to graph (a + b + c) and (d + e) over(year) but I can't figure out
> how to get both in a single graph.
-graph bar- is flexible, but not nearly so flexible as all of Stata. What is
required here is a little good old-fashioned data manipulation.
What Eric can do is duplicate each of his observations and set his 3 variables
(a, b, and c) to 0 in the original observations and his 2 variables (d and e)
to 0 in the duplicate observations. Then, all he need do is create a bar
graph stacking all 5 variables -- half the bars will stack variables a, b, and
c, the other two variables being 0, and the other half of the bars will stack
variables d and e.
Let's use the Klein data from the [R] reg3 entry, mainly because it has short
names. Eric's a, b, and c will be w, p, and t; and his d, and e will be y and
c. (I am too lazy to rename the variables.) We keep the first 9 observations
to match Eric's data.
. webuse kleinabr
. keep in 1/9
Now, expand the data to duplicate each observation and create a variable to
label the original and duplicate observations,
. expand 2
. gen barname = cond(_n <= 9 , "my 2 var" , "my 3 vars")
Replace the set of three variables to stack with 0 in half the observations.
. replace w = 0 in 1/9
. replace p = 0 in 1/9
. replace t = 0 in 1/9
Replace the set of two variables to stack with 0 in the other half of the
observations.
. replace y = 0 in 10/l
. replace c = 0 in 10/l
Graph the 5 variables over the bar identifier variable (barname) and year.
(We will use horizontal bars, -hbar-, because they look better with so many
labels).
. gr hbar w p t y c , stack over(barname) over(year)
The graph described above is prettier if we place all the 2-variable bars
together and all the three variable bars together, though I think Eric wanted
the first graph.
. gr hbar w p t y c , stack over(year) over(barname)
Finally, adorn graph to taste.
-- Vince
[email protected]
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