[R] lme in R and Splus

[Michael Fugate]

Good Day,

Included below is some code to generate data and to fit a mixed effects
model to this fake data.  The code works as expected when I call the
function "lme" in Splus but not in R.  

The error message from calling lme in R is: 
"Error in getGroups.data.frame(dataMix, groups) :
        Invalid formula for groups"

I installed the nlme package for R around 20 August 2003. 

Thanks in advance.

System information:

Splus:
Version 6.1.2 Release 2 for Sun SPARC, SunOS 5.6 : 2002

R:
platform i686-pc-linux-gnu
arch     i686
os       linux-gnu
system   i686, linux-gnu
status
major    1
minor    7.1
year     2003
month    06
day      16
language R



############## BEGINNING OF CODE ###########################
# a fake dataset to make the bumps with
nn <- 30  # of data points
mm <- 7   # number of support sites for x(s)
# create sites s
ss <- seq(1,10,length=nn)
# create the data y
e1 <- rnorm(nn,sd=0.1)
e2 <- cos(ss/10*2*pi*4)*.2
yy <- sin(ss/10*2*pi)+e2+e1
plot(ss,yy)

# locations of support points
ww <- seq(1-2,10+2,length=mm)
# width of kernel
sdkern <- 2

# create the matrix KK
KK <- matrix(NA,ncol=mm,nrow=nn)
for(ii in 1:mm){
KK[,ii] <- dnorm(ss,mean=ww[ii],sd=sdkern)
}

# create a dataframe to hold the data
df1 <- data.frame(y=yy,K=KK,sub=1)
df1$sub <- as.factor(df1$sub)

# now fit a mixed model using lme
a1 <- lme(fixed= y ~ 1,
          random= pdIdent(~KK-1),
          data=df1,na.action=na.omit)

# obtain and plot the fitted values
a1p <- as.vector(predict(a1,df1))
lines(ss,a1p,lty=1)

##################### END OF CODE ######################################3

-- 
*********************************************************************
| Michael Fugate                         Temp Phone: (505) 665-1817 |
| Statistical Sciences Group, D-1                                   |
| Los Alamos National Laboratory         email: fugate at lanl.gov     |
| Los Alamos, NM 87545                                              |
| Mail Stop: F600                                                   |