Frank

Frank has asked 20 questions and find answers to 499 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

replace every other space with new line
Calculating overlap (and distance measures) for categorical variables in R
Take first non-0 value or last 0 value if that's all there is
Looping through rows using lapply with a conditional
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?