Skip to content

Question about lmer

2 messages · Julia Proudnikova, Douglas Bates

#
Hello,

We have a problem with function lmer. This is our code:

Get_values<-function(ff_count, fixed_factors, rf_count, random_factors, y_values)
{       
  SA<-matrix(as.array(c(fixed_factors, random_factors)), ncol=3)
  data<-as.data.frame(SA)
  y<-as.array(y_values)

  dd<-data.frame(SA)
  for(i in 1:(ff_count+rf_count)){
    dd[,i]<-as.factor(data[,i])
  }
  
  fit_full=lmer(y~dd[,1]+dd[,2]+(1|dd[,3]),method="ML")    
  fit_full
}

A<-c(0,0,0,0,1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0,1,1,1,1)
B<-c(0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1)
C<-c(0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1)
Y<-c(5,3,4,1,1,2,6,1,5,3,7,1,2,3,1,1,5,3,4,1,1,2,6,1,5,3,7,1,2,3,1,1)
r<-Get_values(2, c(A,B),1,c(C),Y)
r 

R output:
Error in inherits(x, "factor") : object "dd" not found

Can this function work with random array? Because this code is
working:

D<-as.factor(data[,3])
fit_full=lmer(y~dd[,1]+dd[,2]+(1|D),method="ML")
#
On 6/18/07, Julia Proudnikova <prudnikova at itcwin.com> wrote:
The full explanation of why lmer fails to find dd has to do with the
way names are resolved in a call to model.frame.  However, there may
be a way to solve your problem by redesigning your function so you
don't need to worry about what model.frame does.

Why not pass the data as a data frame and pass the names of the fixed
factors, random factors and response variable as character strings?
Your current design of creating a matrix, then converting it to a data
frame then converting numeric variables back to factors is a bit
convoluted.

If you knew that you were only going to have one random factor you
could generate the formula as

substitute(y ~ ff + (1|rf), list(y = as.name(y_name), ff =
parse(paste(ff_names, collapse = "+")), rf = as.name(rf_name))

It gets a bit trickier with multiple random factors.

Having said all this, it does appear that the call to model.frame
inside lmer is getting the wrong environment from the formula and I
will correct that.

If you need more detail about the redesign I am suggesting, feel free
to contact me off-list.