refer to previous row

[hunluuu947]

Hi I would like to calculate the AUC following the formula below.

In order to do this I need to use the data from the previous row. I wrote my code like this:

However the output data is missing the AUC for the second row like below

How could I fix it?

[PaigeMiller]

Don't include LAG in an IF statement or the ELSE clause.

Example:

prev_value=lag(value);
if x>5 then z=value;
else if x<=5 then z=prev_value;

[hunluuu947]

thank you so much!