1. Try using set.seed for better reproducibility.
2. Does this really work for you? I get
mydf - data.frame(x, y,id)
mod2-lme(y ~ x + x*(x-1), random=~x|id,
+ data=mydf)
Error in lme.formula(y ~ x + x * (x -1), random = ~x | id, data = mydf) :
nlminb problem, convergence error code = 1
message = iteration limit reached without convergence (9)
Enter a frame number, or 0 to exit
1: lme(y ~ x + x * (x -1), random = ~x | id, data = mydf)
2: lme.formula(y ~ x + x * (x -1), random = ~x | id, data = mydf)
Kevin
On Sat, Mar 19, 2011 at 6:16 AM, Federico Bonofiglio bonori...@gmail.comwrote:
Hi Dears,
When I introduce an interaciton in a piecewise model I obtain some quite
unusual results.
If that would't take u such a problem I'd really appreciate an advise from
you.
I've reproduced an example below...
Many thanks
x-rnorm(1000)
y-exp(-x)+rnorm(1000)
plot(x,y)
abline(v=-1,col=2,lty=2)
mod-lm(y~x+x*(x-1))
summary(mod)
yy-predict(mod)
lines(x[order(x)],yy[order(x)],col=2,lwd=2)
#--lme
#grouping factor, unbalanced
g-as.character(c(1:200))
id-sample(g,size=1000,replace=T,
prob=sample(0:1,200,rep=T))
table(id) #unbalanced
mod2-lme(y~x+x*(x-1),random=~x|id,
data=data.frame(x,y,id))
summary(mod2)
newframe-data.frame( #fictious id
id=fictious,
x)
newframe[1:5,]
#predictions
yy2-predict(mod2,level=0, newdata=newframe)
lines(x[order(x)],yy2[order(x)],col=blue,lwd=2)
# add variable in the model
z-rgamma(1000,4,6)
mod3-lme(y~x+x*(x-1)+z
,random=~x|id,
data=data.frame(x,y,z,id))
summary(mod3)
#new id
newframe2-data.frame( #fictious id
id=fictious,
x,
z)
#predict
yy3-predict(mod3,level=0, newdata=newframe2)
lines(x[order(x)],yy3[order(x)],col=green,lwd=2)
# ADD INTERACTION z:x
mod4-lme(y~x+x*(x-1)+
z+
z:x+
z:x*(x-1)
,random=~x|id,
data=data.frame(x,y,z,id))
#predict
yy4-predict(mod4,level=0, newdata=newframe2)
lines(x[order(x)],yy4[order(x)],col=violet,lwd=2) #something bizarre
#starts to happen
#in the predicted values
# they begin to jiggle around the straight line
--
*Little u can do against ignorance,it will always disarm u:
is the 2nd principle of thermodinamics made manifest, ...entropy in
expansion.**But setting order is the real quest 4 truth, ..and the
mission of a (temporally) wise dude.
*
[[alternative HTML version deleted]]
__
R-help@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.
[[alternative HTML version deleted]]
__
R-help@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.
