tomhopper

##' Modifies 'data' by adding new values supplied in newDataFileName
##'
##' newDataFileName is expected to have columns 
##' c(lookupVariable,lookupValue,newVariable,newValue,source)
##' 
##' Within the column 'newVariable', replace values that
##' match 'lookupValue' within column 'lookupVariable' with the value
##' newValue'.  If 'lookupVariable' is NA, then replace *all* elements
##' of 'newVariable' with the value 'newValue'.
##'

tomhopper

library(dplyr)

# create a dummy dataframe with 100,000 groups and 1,000,000 rows
# and partition by group_id
df <- data.frame(group_id=sample(1:1e5, 1e6, replace=T),
                 val=sample(1:100, 1e6, replace=T)) %>%
      group_by(group_id)

# filter rows with a value of 1 naively
system.time(df %>% filter(val == 1))

tomhopper

# Create 2 replicates of 5 "words" generated from random characters,
# each "word" 5 - 15 characters long, with word length following a 
# poisson distribution.
rep(replicate(5, paste(sample(letters, round(rpois(5000, lambda = 3)+5, 0), replace = FALSE), collapse = "")), 2)

# Sample output:
# [1] "rfexnwyjst" "vwtadhjnly" "ztfgvldo"   "tmerol"     "mcqhosap"   "rfexnwyjst" "vwtadhjnly" "ztfgvldo"   "tmerol"    
#[10] "mcqhosap"