Singular design matrix in rq
Have you looked at the result of bs(raw_data[,i], df=15) ? If there are not many unique values in the input there will be a lot of NaN's in the output (because there are repeated knots) and those NaN's will cause rq() to give that message. E.g.,
d <- data.frame(y=sin(1:100), x4=rep(1:4,each=25), x50=rep(1:50,each=2)) rq(data=d, y ~ bs(x4, df=15), tau=.8) # using x50 "works"
Error in rq.fit.br(x, y, tau = tau, ...) : Singular design matrix
with(d, bs(x4, df=15))
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
[1,] 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
[2,] 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
[3,] 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
...
[98,] 0 0 0 0 0 0 0 0 0 0 0 NaN NaN NaN NaN
[99,] 0 0 0 0 0 0 0 0 0 0 0 NaN NaN NaN NaN
[100,] 0 0 0 0 0 0 0 0 0 0 0 NaN NaN NaN NaN
attr(,"degree")
[1] 3
attr(,"knots")
7.692308% 15.38462% 23.07692% 30.76923% 38.46154%
1 1 1 2 2
46.15385% 53.84615% 61.53846% 69.23077% 76.92308%
2 3 3 3 4
84.61538% 92.30769%
4 4
attr(,"Boundary.knots")
[1] 1 4
attr(,"intercept")
[1] FALSE
attr(,"class")
[1] "bs" "basis" "matrix"
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Jonathan Greenberg Sent: Tuesday, April 16, 2013 12:58 PM To: r-help; Roger Koenker Subject: [R] Singular design matrix in rq Quantreggers: I'm trying to run rq() on a dataset I posted at: https://docs.google.com/file/d/0B8Kij67bij_ASUpfcmJ4LTFEUUk/edit?usp=sharing (it's a 1500kb csv file named "singular.csv") and am getting the following error: mydata <- read.csv("singular.csv") fit_spl <- rq(raw_data[,1] ~ bs(raw_data[,i],df=15),tau=1)
Error in rq.fit.br(x, y, tau = tau, ...) : Singular design matrix
Any ideas what might be causing this or, more importantly, suggestions for how to solve this? I'm just trying to fit a smoothed hull to the top of the data cloud (hence the large df). Thanks! --jonathan -- Jonathan A. Greenberg, PhD Assistant Professor Global Environmental Analysis and Remote Sensing (GEARS) Laboratory Department of Geography and Geographic Information Science University of Illinois at Urbana-Champaign 607 South Mathews Avenue, MC 150 Urbana, IL 61801 Phone: 217-300-1924 http://www.geog.illinois.edu/~jgrn/ AIM: jgrn307, MSN: jgrn307 at hotmail.com, Gchat: jgrn307, Skype: jgrn3007 [[alternative HTML version deleted]]
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