data(iris)
prop2sample<-.5
rowIDs<-sample(1:nrow(iris), as.integer(prop2sample*nrow(iris)))
iris.sample<-iris[rowIDs,]
head(iris.sample)
##     Sepal.Length Sepal.Width Petal.Length Petal.Width   Species
## 28           5.2         3.5          1.5         0.2    setosa
## 33           5.2         4.1          1.5         0.1    setosa
## 37           5.5         3.5          1.3         0.2    setosa
## 131          7.4         2.8          6.1         1.9 virginica
## 9            4.4         2.9          1.4         0.2    setosa
## 18           5.1         3.5          1.4         0.3    setosa
rowIDs<-sample(1:nrow(iris), as.integer(prop2sample*nrow(iris)), replace = TRUE)
iris.sample.r<-iris[rowIDs,]
head(iris.sample.r)
##     Sepal.Length Sepal.Width Petal.Length Petal.Width    Species
## 80           5.7         2.6          3.5         1.0 versicolor
## 31           4.8         3.1          1.6         0.2     setosa
## 89           5.6         3.0          4.1         1.3 versicolor
## 105          6.5         3.0          5.8         2.2  virginica
## 63           6.0         2.2          4.0         1.0 versicolor
## 74           6.1         2.8          4.7         1.2 versicolor