Short answer: No, it is not possible. But other solutions are easy.
For those following along, -qplot- is a program downloadable from the
Stata website given its publication in the Stata Journal. -search qplot-
for locations.
-qplot- is best thought of as a considerable generalisation of the
official -quantile- command (with one cosmetic exception: -qplot- does
not show the tilted reference line that is a -quantile- default).
-qplot- plots ordered or sorted values (with some flexibility about how
sorted) versus cumulative fraction or rank (ditto), or indeed, via the
-xvariable()- option, versus any specified variable.
Shehzad's problem is different. Shehzad wants to plot something else
versus the ranks of (e.g.) income. This is not among the possibilities
of -qplot- at present. It might be accommodated by adding a
-yvariable()- option, but I am reluctant to do that. There is a fine
line between adding another feature that somebody might want and making
a program yet more complicated to use and understand, and indeed there
is, in this case, a risk of muddying the purpose of the program.
As previously implied, Shehzad's solution should be at worst two lines'
worth. Apart from what you can with -glcurve- (-findit- for locations),
there is a more direct solution:
egen rank = rank(income)
twoway <whatever> <somethingelse> rank
There is much scope for modifying that simple recipe. For example, the
usual convention is that the richest person is #1, and so forth, and
that is achievable in a flash:
egen rank = rank(-income)
Further, -egen, rank()- has options. Mapping to variously defined
cumulative fractions is also a step away. There is an FAQ on that:
FAQ . . . . . . . . . . Calculating percentile ranks or plotting
positions
7/02 How can I calculate percentile ranks?
How can I calculate plotting positions?
http://www.stata.com/support/faqs/stat/pcrank.html
Shehzad seems to be hankering after a one-line alternative to this
two-line solution.
That's achievable with some programming, but as I said earlier I don't
think it exists at present.
Nick
[email protected]
Shehzad Ali
Thanks, Nick. This is a very useful command to know. Now my question is:
using qplot I want to generate a graph of y-variable which is rank
ordered
by x-variable (obviously different from Pen's parade). If I used the
option
- xvariable - in - qplot -, it produces an x-axis over the entire range
of x
variable but I am interested only in x-rank to sort my y-var. Is it
possible
to do this using qplot?
Nick Cox
You can make this possible in one line by writing a wrapper for those
commands, but I am not aware of any way to do that which is already
available. -qplot- (-search- for locations) allows plots of income
versus income rank, including a kind of graph which income people
associate with Jan Pen (although the same idea goes back much earlier).
Shehzad Ali
I want to create a twoway graph (like spike or dropline) where the
x-axis
is a rank variable (based on say income) and y-axis is the other
variable
of interest (say health_pay). A simple command - twoway spike health_pay
income - spread the x-axis over the whole range of income but I am
interested in income rank and not income itself.
I know one way to do it is to generate income rank variable using -
glcurve
- and then plotting the rank_var against health_pay but I was wondering
if
there was a direct method.
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