I am having trouble running nlme.  Here is the relevant snippet of my
code.  Any ideas?

    df <- data.frame(phen = phen.info.box[,2], hap = as.factor(mouse.haps),
strain = as.factor(mouse.strains))

    fit <- nlme(model = phen ~ hap + strain,
                data = df,
                fixed = hap + strain ~ 1,
                random = strain ~ 1,
                start = rep(0, nrow(df)),
                correlation = K)

The error is:

Error in getGroups.data.frame(dataMix, eval(parse(text = paste("~1",
deparse(groups[[2]]),  :
  invalid formula for groups


-Robert

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