[R] How to correct my error message

[varin sacha]

Dear R-experts,

Here below my R code. The warning message is not a problem to me but there is an error message more problematic. I understand the error message but I don't know if it is possible to correct the error and if yes, how to correct it.

Many thanks.


n <- 60
b <- runif(n, 0, 5)
a <- runif(n, 0, 5)
z <- rnorm(n*0.95,2,3) + rnorm(n*0.05,2,9)
y_model <- 0.1 * b - 0.5 * z - a + 10
y_obs <- y_model +c( rnorm(n*0.95, 0, 0.1), rnorm(n*0.05, 0, 0.5) )
df<-data.frame(b,a,z,y_obs)