Subset And Apply Problems

Tom Martens explains a class of generic data processing problems:

Subset and Apply means that I have a dataset of some rows where due to some conditions all the rows have to be put into a bucket and then a function has to be applied to each bucket.

The simple problem can be solved by a GROUP BY using T-SQL, the not so simple problem requires that all columns and rows of the dataset have to be retained for further processing, even if these columns are not used to subset or bucket the rows in your dataset.

One quick example of this is running totals of orders for each customer, which Tom answers using T-SQL, R, and Power BI.  Click through for those three solutions.

Related Posts

Power BI Violin Plots

Meagan Longoria shows off a violin plot custom visual in Power BI: A violin plot is a nifty chart that shows both distribution and density of data. It’s essentially a box plot with a density plot on each side. Box plots are a common way to show variation in data, but their limitation is that you can’t […]

Read More

No Type Equivalence In M

Imke Feldmann notes an oddity in types in Power Query: But this function will not return any matches. I also tried out a (potentially) slower version using Table.SelectColumns(Types, each [Value] = x[Types]) – but still no match.  What I found particularly frustrating here was, that in some cases, these lookups or filters on type-columns worked. […]

Read More

Categories

January 2017
MTWTFSS
« Dec Feb »
 1
2345678
9101112131415
16171819202122
23242526272829
3031