加速 R 中的“for”循环

Question

Combined has 6713 rows and bids has 7656334 rows:

i = 1
for(i in 1:length(combined$bidder_id)){
  combined$no_of_bids[i] = count(bids[bids$bidder_id == combined$bidder_id[i],])
  i = i + 1
}

It takes about 30 mins to run this code. Any suggestion to speed it up?

Answer 1

In this case loop is slower then other R functions

For example, in tidyverse style group_by() does the job much faster

library(tidyverse)

bids <- tibble(bidder_id=sample(1:1000, 100000, replace = TRUE))

combined <- bids %>% 
  group_by(bidder_id) %>% 
  summarise(no_of_bids = n())

Answer 2

Should be:

library(dplyr)
left_join(combined,
          count(bids, bidder_id),
          by = 'bidder_id')

Next question please post a reproducible example.