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SO_17844143
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require(qdapTools) | |
set.seed(1L) | |
x = data.frame(zip=sample(1e6), market=0L) | |
y = data.frame(market=sample(20, 2000, TRUE), zip=sample(1e6, 2000, FALSE)) | |
#### this line takes a long time... Tyler any ideas why? | |
x$market = lookup(x$zip, y[, 2:1]) | |
#### | |
# I think the actual answer is: | |
system.time({ | |
idx1 = match(x$zip, y$zip) | |
idx2 = which(!is.na(idx1)) | |
x$market[idx2] <- y$market[idx1[idx2]] | |
}) | |
# takes 0.085 seconds | |
## here's a data.table solution using joins - although this is not necessary here: | |
require(data.table) | |
set.seed(1L) | |
x = data.frame(zip=sample(1e6), market=0L) | |
y = data.frame(market=sample(20, 2000, TRUE), zip=sample(1e6, 2000, FALSE)) | |
system.time({ | |
setDT(x) | |
setDT(y) | |
setkey(x, zip) | |
setkey(y, zip) | |
x[y, market := i.market] | |
}) | |
## takes 0.094 seconds | |
## here's using match and `:=` in data.table | |
require(data.table) | |
set.seed(1L) | |
x = data.frame(zip=sample(1e6), market=0L) | |
y = data.frame(market=sample(20, 2000, TRUE), zip=sample(1e6, 2000, FALSE)) | |
system.time({ | |
idx = match(x$zip, y$zip, nomatch=0L) | |
setDT(x)[idx != 0L, market := y$market[idx]] | |
}) | |
## takes 0.58 seconds. |
Note to self: cleaned up noise, and updated benchmarks. Benchmark on relatively large data - 200 million rows and 50k unique groups, which illustrates the impact of the copy to replace NAs with 0's in dplyr
after left_join
:
On big data benchmark:
With data.table v1.9.6+
require(data.table)
N = 200e6L
K = 50e3L
DT = function() {
setDT(x)[, market := 0L][setDT(y), market := i.market, on="zip"]
}
set.seed(1L)
x <- data.frame(zip=sample(N))
y <- data.frame(market=sample(20, 2000, TRUE), zip=sample(N, K, FALSE))
gc()
system.time(DT()) # all heap & anonymous VM, total bytes = 1.81GB, persistent = 1.01GB
#10.862 0.545 11.520
With dplyr v0.4.3.9001:
require(dplyr)
N = 200e6L
K = 50e3L
DPLYR = function() {
x <- left_join(x,y, by = 'zip') %>% mutate(market = replace(market, which(is.na(market)), 0L))
}
set.seed(1L)
x <- data.frame(zip=sample(N))
y <- data.frame(market=sample(20, 2000, TRUE), zip=sample(N, K, FALSE))
gc()
system.time(DPLYR()) # All heap & anonymous VM, total bytes = 9.22GB, persistent = 5.22GB
#24.249 3.341 28.946
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I did a quick benchmark of the 3 approaches
The winner is! Indexing