[R] sink to file

[Urs Wagner]

Hello

I would like to use the source(command)  and write the output into a file.
I am using

outputfile=file("output.txt", open="wt")
sink(outputfile, type="output")
source("input.R", echo=TRUE)

Unfortunately the result has prompted commands. How can I avoid the 
prompted commands data(iris), ...?

Thanks

 > data(iris)
 > dataset = iris
 > options(width = 50)
 > summary(dataset)
  Sepal.Length    Sepal.Width     Petal.Length 
 Min.   :4.300   Min.   :2.000   Min.   :1.000 
 1st Qu.:5.100   1st Qu.:2.800   1st Qu.:1.600 
 Median :5.800   Median :3.000   Median :4.350 
 Mean   :5.843   Mean   :3.057   Mean   :3.758 
 3rd Qu.:6.400   3rd Qu.:3.300   3rd Qu.:5.100 
 Max.   :7.900   Max.   :4.400   Max.   :6.900 
  Petal.Width          Species 
 Min.   :0.100   setosa    :50 
 1st Qu.:0.300   versicolor:50 
 Median :1.300   virginica :50 
 Mean   :1.199                 
 3rd Qu.:1.800                 
 Max.   :2.500