Turn weekly data into monthly data

[trevhill]

I have years of railroad data by week (amount of rail tonnes shipped per week)

Ex:

week 1 597
week 2 588
week 3 600
.....
......
......
......
week 54 783

I would like to setup a column that translates the monthly data into weekly data. I.e

Month 1
Month 2
Month 3
Month 4.

My ultimate goal is to calculate the month-over-month change.

Any ideas on how to do this easily?

 

[Andrew Poulsom]

What determines which weeks go into which months?

 

[Asator]

Why not use a pivot table?