Frank

Frank has asked 20 questions and find answers to 483 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

Why do I get a " Invalid .internal.selfref detected" warning (but no output) even if I am not using list(),key<-, names<-, or attr<-?
Assign a data.table column to a variable in R
Vectorization of for-loop for calculations between two datasets in R
Sum of all pairwise row products as a two way matrix
When grouping by all columns in a data.table, .SD is empty
Permute/randomize rows within a column independently
Group by ID, each element of the new table is a vector
Reshaping data using tidyr
aggregate data.table to rows of intervals of original values
Divide Groups by # of samples in each group in R