How to add new column

[santoshbs]

Is there a way to add a new column to a datatable that is based on a function of another column?

[st-pasha]

Yes, you can either use an assignment statement, or the update() function:

DT["newcol"] = <expression> # or
DT[:, update(newcol=<expression>)]

where <expression> is any formula involving other columns. For example:

DT[:, update(Revenue = f.Quantity * f.Price)]

[santoshbs]

I am still failing to understand the datatable equivalent of the following pandas dataframe code:

df['col2']= df.apply(lambda row: my_function(row['col1']), axis=1)

[st-pasha]

Currently there is no direct equivalent of the pandas apply function, though the same effect can be achieved by converting the column into a python list, applying the function to the list, and then converting back into a Frame:

df['col2'] = dt.Frame([my_function(x)  for x in df['col1'].to_list()[0]])