Accumulate column data

Question

How do I use the lag operator to add up data on a row wise basis?  That is, I want to accumulate data from column tair in a new column called chilling degree if the tair value is > 5.

tair   chilling degree
5        5
7       5
5       10

unknown · Answer

If you want to simply accumulate values in a column, you don't necessarily need the lag operator.  If you want to accumulate data (get a cumulative sum) for a column called "tair", do the following:

1.  Create a new column.  In this example, I call it "total".
2.  Put the following formula in the new column:
(ignore this line)

The formula takes the value of tair in the current row, and adds it to the previous value of total, thus creating a cumulative sum.

If you only want to accumulate the values if they are greater than or equal to 5, then use the formula:

(ignore this line)

The formula looks at the current value of tair, and if it is less than 5, instead of adding tair, it adds 0.

afterword · Answer

I don't know the answer to this question, but it sounds like you're working with building energy data.  Am I right?  That's my field as well so I'd be happy to trade scripts and files with you.