How can i subtract current values from previous week values?
Hello,
I am trying to subtract current week values with previous week values and have the ability for this to update each week. How would I do this in Magic ETL? A lag function?
So 5-19 week would subtract from 5-12 week and then next week I would like to see 5-26 week subtract from 5-19.
Thanks,
Garrett
Best Answers
-
Assuming your data will always be grouped by week, you could use a lag function. You would use a Rank & Window tile to achieve this in ETL. One thing to keep in mind, is that lag will always go to the last value, so if you are missing data for a week, it would go back 2 weeks. If you want to avoid this, you will need to fill in your missing weeks by joining up a date dimension table.
Here is an example of how you could set it up.
Which yields the following
David Cunningham
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@gbrown it looks like you have this set up to lag 300 rows. Is that what you want?
You can always test the output by running a preview in ETL, and then checking the output to see if it matches what your desired output is.
David Cunningham
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I'd recommend restructuring your data with a custom date offset so you can easily calculate the prior week. I've done a write up on it here:
**Was this post helpful? Click Agree or Like below**
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Answers
-
Assuming your data will always be grouped by week, you could use a lag function. You would use a Rank & Window tile to achieve this in ETL. One thing to keep in mind, is that lag will always go to the last value, so if you are missing data for a week, it would go back 2 weeks. If you want to avoid this, you will need to fill in your missing weeks by joining up a date dimension table.
Here is an example of how you could set it up.
Which yields the following
David Cunningham
** Was this post helpful? Click Agree 😀, Like 👍️, or Awesome ❤️ below **
** Did this solve your problem? Accept it as a solution! ✔️**1 -
Thanks. Is this how I would set up the lag function? @david_cunningham
0 -
@gbrown it looks like you have this set up to lag 300 rows. Is that what you want?
You can always test the output by running a preview in ETL, and then checking the output to see if it matches what your desired output is.
David Cunningham
** Was this post helpful? Click Agree 😀, Like 👍️, or Awesome ❤️ below **
** Did this solve your problem? Accept it as a solution! ✔️**0 -
I'd recommend restructuring your data with a custom date offset so you can easily calculate the prior week. I've done a write up on it here:
**Was this post helpful? Click Agree or Like below**
**Did this solve your problem? Accept it as a solution!**0
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