Arun

Arun has asked 18 questions and find answers to 639 problems.

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Arun questions

understanding optimisation messages on assignment by reference in a data.table
When does setting 'perl=TRUE' in 'strsplit' does not work (as intended or at all)?
Warning message: in rbindlist(allargs) : NAs introduced by coercion: possible bug in data.table?
unexpected output from aggregate
Using 'mutate_' to sum a bunch of columns row-wise
Why is subsetting on a "logical" type slower than subsetting on "numeric" type?
rbindlist two data.tables where one has factor and other has character type for a column
DT[!(x == .)] and DT[x != .] treat NA in x inconsistently
Why does "^" on a data.frame return a matrix instead of a data.frame like "*" does?

Arun answers

Speed up vector-lookup for data.table
rbind 2 vectors of different lengths by their names
Creating new column in data frame in R by comparing 2 existing columns and then deleting the latter
How to select the first n rows of each group in specified columns (after a join)?
Is there a way to replace column values on matching rows while joining one data.frame to another?
melt and merge several files into a single database using R
R merge a particular column from one data frame to another according to its reference column
data.table confusion using rollends argument of rolling join
"dims [product 0] do not match the length of object" error in R when using daply for frequency counts
Optimal way in data.table to make multiple columns from vectors of column name strings