Hi, there. I am back to the knowledge well!
Using pandas I have a dataframe with Date, Item#, Qty and 12 months of data. I want to do a std dev calc to understand the monthly variability for each Item#.
The problem is for many Item#'s the sales are very sporadic: I may only sell Item XYZ in Feb and Mar, and zero the rest of the months of the year.
I am using this code to do the heavy lifting:
df.groupby('Item#').resample('M').sum()
For some Item#'s it is forcing zeros into the empty months (GOOD!), but in many cases it is just showing, say, two months of data, instead of 12, which then makes the std dev calculation incorrect.
Can someone help me understand why this erractic behaviour of the resample method? How can I workaround this problem?
Many thanks in advance for your help!
Using pandas I have a dataframe with Date, Item#, Qty and 12 months of data. I want to do a std dev calc to understand the monthly variability for each Item#.
The problem is for many Item#'s the sales are very sporadic: I may only sell Item XYZ in Feb and Mar, and zero the rest of the months of the year.
I am using this code to do the heavy lifting:
df.groupby('Item#').resample('M').sum()
For some Item#'s it is forcing zeros into the empty months (GOOD!), but in many cases it is just showing, say, two months of data, instead of 12, which then makes the std dev calculation incorrect.
Can someone help me understand why this erractic behaviour of the resample method? How can I workaround this problem?
Many thanks in advance for your help!