Making a loop for lme() in r

Question

I am trying to use lme function from nlme package inside a for loop. I have tried (almost) everything now, but without any luck. Without the loop my lme function are working

Answer 1

Without knowing your data, conceptually it should be sth like that

df <- data.frame(lipid = rep(c(LETTERS[1:4]), each = 4), x1 = c(rnorm(16, 10, 1)), x2 = c(rnorm(16, 20, 5) ))
    df

for (i in levels(df$lipid)){
  print(paste("MODEL", i, sep = ""))
  df1 = subset(df, lipid == i)
  model <- lm(x1~x2, data = df1 )
  print(summary(model)$coef)
}