\begin{Schunk}
\begin{Sinput}
 xval <- 0:10
 par(mfrow=c(2,2))
 y <- dpois(xval, lambda=0.5)
 names(y) <- xval
 barplot(y, main="lambda=0.5", col = "white")
 y <- dpois(xval, lambda = 1.0)
 names(y) <- xval
 barplot(y, main="lambda=1.0", col = "white")
 y <- dpois(xval, lambda=1.5)
 names(y) <- xval
 barplot(y, main="lambda=1.5", col = "white")
 y <- dpois(xval, lambda=2.0)
 names(y) <- xval
 barplot(y, main="lambda=2.0", col = "white")
 par(mfrow=c(1,1))
\end{Sinput}
\end{Schunk}
