Sample random rows in DataFrame in R

Question

I am having a problem in finding a proper function that would return specific number of rows picked randomly without replacement from  a data frame?

Answer 1

First we should have some data:

df1<-data.frame(matrix(rnorm(20), nrow=10))
> df1
           X1          X2
1  -0.5996083  0.80017687
2  -0.1294107 -0.16393097
3   0.8867361  1.24291877
4  -0.1513960 -0.93438506
5   0.3297912  0.39370865
6  -3.2273228  0.40363146
7  -0.7717918 -0.88643672
8   0.2865486 -1.31893760
9  -1.2205120  0.02884391
10  0.4345504 -0.43212979

Then select some rows at random:

df1[sample(nrow(df1), 3), ]
          X1         X2
10 0.4345504 -0.4321298
5  0.3297912  0.3937087
8  0.2865486 -1.3189376