Weighted sampling in R

Question

I have a data frame data. At each row i have assigned a weight that is in data$ww. Now I would like to make a sample new_data

Answer 1

Use the prob argument of sample():

samp_idx <- sample(seq_len(nrow(data)), nsample, prob=data$ww)
new_data <- data[samp_idx, ]

Something like this. Running time is

# user  system elapsed 
# 0.015   0.000   0.014 

versus your version:

# user  system elapsed 
# 4.278   0.007   4.290