f
by()
Calculate the sum of all values for each column in the frame.
Frame
The frame will have one row and the same number/names of columns as in the current frame. All the columns will have float64 stype. For non-numeric columns this function returns NA values.
float64
.sum1() – similar to this method, but operates on a single-column frame only, and returns a scalar value instead of a Frame.
.sum1()
dt.sum() – function for calculating the sum of all the values in a column or an expression; can also be applied per-group.
dt.sum()