[R] Fitting a Triangular Distribution to Bivariate Data

[Jonathan P Daily]

I don't know if any specific package has a triangular distribution, but I 
know you can fit a model using first degree b-splines with a single knot.

library(splines)
?bs
x <- 1:100
y <- rnorm(100, ifelse(x <50, x, 100-x), 15)
fit <- lm(y ~ bs(x, knots = 50, degree = 1))

--------------------------------------
Jonathan P. Daily
Technician - USGS Leetown Science Center
11649 Leetown Road
Kearneysville WV, 25430
(304) 724-4480
"Is the room still a room when its empty? Does the room,
 the thing itself have purpose? Or do we, what's the word... imbue it."
     - Jubal Early, Firefly

r-help-bounces at r-project.org wrote on 12/22/2010 01:19:16 PM:

> [image removed] 
> 
> [R] Fitting a Triangular Distribution to Bivariate Data
> 
> David Bapst 
> 
> to:
> 
> r-help
> 
> 12/22/2010 04:04 PM
> 
> Sent by:
> 
> r-help-bounces at r-project.org
> 
> Hello,
> I have some xy data which clearly shows a non-monotonic, peaked
> triangular trend. You can get an idea of what it looks like with:
> 
> x<-1:20
> y<-c(2*x[1:10]+1,-2*x[11:20]+42)
> 
> I've tried fitting a quadratic, but it just doesn't the data-structure
> with the break point adequately. Is there anyway to fit a triangular
> or 'tent' function to my data in R?
> 
> Some sample code would be appreciated; I'm not new to R, but I
> sometimes have difficulty understanding the model-fitting functions
> (finally figured out how to extrapolate with predict() today!)
> 
> Thanks!
> -Dave Bapst, UChicago
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.