How to create a new column by dividing two columns in Graphlab SFrame?

Question

Given a Graphlab SFrame as such:

+-------+------------+---------+-----------+
| Store |    Date    |  Sales  | Customers |
+-------+------------+---------+-----------+
|   1   | 2015-07-31 |  5263.0 |   555.0   |
|   2   | 2015-07-31 |  6064.0 |   625.0   |
|   3   | 2015-07-31 |  8314.0 |   821.0   |
|   4   | 2015-07-31 | 13995.0 |   1498.0  |
|   3   | 2015-07-20 |  4822.0 |   559.0   |
|   2   | 2015-07-10 |  5651.0 |   589.0   |
|   4   | 2015-07-11 | 15344.0 |   1414.0  |
|   5   | 2015-07-23 |  8492.0 |   833.0   |
|   2   | 2015-07-19 |  8565.0 |   687.0   |
|   10  | 2015-07-09 |  7185.0 |   681.0   |
+-------+------------+---------+-----------+
[986159 rows x 4 columns]

How do I add an "Sales per Customer" column by dividing the Sales by the Customers for each row?

I have tried the following but they don't work ( sf is my SFrame :

sf['salespercustomer'] = sf.apply(lambda x: sf['Sales']/sf['Customers'])

Interestingly I get an output of a SArray with:

sf['Sales'] / sf['Customers']

But that doesn't really help to add the column back to the sf , so this does't work =( :

sf['salescustomer'] = sf['Sales'] / sf['Customers']

Answer 1

The last line of code should do the trick, but you said your SFrame is called sf , not train . When I try it with sf it works fine.

Answer 2

This is how I would do it.

sf['salespercustomer'] = sf['Sales','Customers'].apply(lambda row: row['Sales']/row['Customers'])

FWIW, your sample passed the entire sf to the apply lambda as parameter x, but you used sf. My understanding is that sf is not known in the lambda function, but the alias to x is.

FWIW, you can do a single column operation like this:

sf['sales25percentdiscount'] = sf['Sales'].apply(lambda x: x*.0.75)

Since only one column is specified, you don't need to specify columns in the lambda function.