[R] finding the intersection of two vectors

Data Analytics Corp. walt at dataanalyticscorp.com
Wed Jul 6 22:43:56 CEST 2011


Suppose I have two vectors, not necessarily the same length (in fact, 
they usually are different lengths): y.1 that has increasing values 
between 0 and 1; y.2 that has decreasing values between 1.0 and 0.  You 
can picture these as being supply (= y.1) and demand (= y.2) curves from 
economics.  I typically plot these vectors on the same graph against a 
common x variable, which happens to be price for what I do.  The price 
variable runs from, say, $0 to $25.  When I plot y.1 and y.2, I've been 
eye-balling a vertical line at a price point where y.1 intersects y.2.  
I'm now tired of eye-balling a line through the intersection -- takes 
too much time to get it right or just close enough.  I can't figure out 
how to find the price value at which the two curves intersect.  Going 
back to the economics interpretation, I want the price where supply 
equals demand.  Any suggestions as to how I can find that price point in 
R?  Any functions that help?




Walter R. Paczkowski, Ph.D.
Data Analytics Corp.
44 Hamilton Lane
Plainsboro, NJ 08536
(V) 609-936-8999
(F) 609-936-3733
walt at dataanalyticscorp.com

More information about the R-help mailing list