Mamoun Benghezal questions

Mamoun Benghezal answers

• How to substract a column by row?
• How to change column in matrix according to another column
• Smooth a density plot so that it doesn't appear saw toothed
• in R, what is the difference between get("abc") and eval(parse(text="abc"))
• R equivalent of SQL SELECT COUNT(*) ... GROUP BY
• How to add horizontal line to xy plot in lattice
• filter R data frame with one column - keep data frame format [duplicate]
• ggplot2: add line for sum of group values at each x
• Determine index of elements in a vector which occur only once
• Avoiding multiple for-loops in R to calculate a matrix