Adding horizontal and vertical lines to functions

[bsc.j.j.w]

Dear all,

I have a small problem and I can't find it documented anywhere, but is it possible in Stata 13.1 to draw a line from a specific tick to the x-axis and y-axis?

In order to clarify what I would like I've constructed the following example:

graph twoway function y=x^2

Now what I would like is at tick (2, 4) to have a line drawn from (2, 0) to (2, 4) (i.e. a vertical line from the x-axis to the tick) and a line drawn from (0, 4) to (2, 4) (i.e. a horizontal line from the y-axis to the tick.

Yours sincerely,

Wen Jun Jie

[Svend Juul]

Two possibilities:

graph twoway function y=x^2 , range(0 3) xline(2) yline(4)

twoway (function y=x^2, range(0 3) dropline(2)) (function y=4, range(0 2))

[bsc.j.j.w]

The first solution (in which you use xline and yline), I've considered, but it will also draw lines past the tick. This is not exactly what I want.
The second solution looks really good and promising, thanks!

I was wondering whether I could automate the calculation of the y-value. In my case the function is rather simple, but I can imagine that if you have a more compllicated function, you wouldn't want to calculate it.