Sven Hohenstein questions

Sven Hohenstein answers

• subsetting dynamically -- subsetting by a variable that is defined in a function
• For each row in data.table, find column name where value == X
• R use str_extract (stringr) to export a string between "_"
• Categorical variables in R - which one does R pick as reference?
• Summary / Aggregate in R without dropping levels
• How to conveniently add a large set of regressors in R?
• Find the index of minimum non negative value in R
• How to create box plot based on min and max alone
• Display duplicate records in data.frame and omit single ones
• plot grouped data in R