[R] Error in hist.default(A) : `x' must be numeric

[Mag. Ferri Leberl]

Dear everybody!
I have load a list A of numbers and want a histogram to be drawn.
on
hist(Y)
the Machine returns:
Error in hist.default(A) : `x' must be numeric
I found out, that the list is of type data.frame.
Y<-as.numeric(Y)
returns
Error in as.double.default(A) : (list) object cannot be coerced to double
What schould I do?
Than you in advance!