Frank

Frank has asked 20 questions and find answers to 495 problems.

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Frank questions

using return list macros with `: list' syntax
fill rows downward for a column with NAs (with R base or data.table)
splitting (1:n)[boolean] into contiguous sequences
accessing Y columns with duplicated names in j of X[Y, j] merges
print the data.table package's .onAttach messages with knitr
Clean, simple function factories in R
Using data.table's .() shortcut in quoted expressions
lapply-ing with the "$" function
Efficiently computing a linear combination of data.table columns
data.table `:=` assignment expressions with dynamic inputs (existing columns) and outputs (new column names)

Frank answers

Strsplit and count occurrences
How to roll sum by conditon?
Sum up cells by some columns
data.table performance not scaling linearly on computing lagged differences of a column by group
Lag value with dates
How to predict the next variable in a row based on current patterns?
Map entries between two data.tables
Splitting a string using variable offset
R data.table update join by reference within function
Loops in R, aggregating data based on different variable