Bookmark and Share

Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down at the end of May, and its replacement, is already up and running.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: Test for significance of the difference between knee locations?

From   Austin Nichols <>
Subject   Re: st: Test for significance of the difference between knee locations?
Date   Fri, 19 Oct 2012 09:48:30 -0400

Jordan Silberman <>:
You need to be a lot more clear about what you want. Below, you seem
to be describing estimation of a kink point, using two linear curves
that meet at one value of x, without discontinuities in the curves but
with a discontinuity in derivatives. Then in the original post you
describe comparing two quadratic curves (presumably with no kinks).
Can you show what you want using a publicly available dataset e.g.
wage as a function of age for union and nonunion:
sysuse nlsw88, clear
tw qfit wage age if union==0||qfit wage age if union==1

On Thu, Oct 18, 2012 at 5:26 PM, Jordan Silberman
<> wrote:
> According to one approach (from Dmitri Kaplan, described here:
> the knee is the x value that minimizes the sum of the squared errors
> of two linear regressions--one modeling all points left of the knee
> and one modeling all points right of the knee. It's an estimate of the
> point at which the slope "turns."
*   For searches and help try:

© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   Site index