Hi - Dave here.

Happy Friday!

Weather stations collect a lot of data!

Summarizing this data in Excel can be tricky because there might be tens of thousands of rows.

In this example, the goal is to summarize a year of granular weather station readings (about 35,000 rows, one every 15 minutes) for Chicago, Illinois, into a daily summary, then a monthly summary. 

The worksheet below shows what the monthly summary looks like. The entire table is generated with a single formula in cell B5.

Using GROUPBY to collapse over 35,000 rows of data

[Download the workbook and read the full explanation]

This is a surprisingly challenging problem in Excel, and the formulas are complex. But it's also a nice example of how Excel's new dynamic array formulas can be used to solve hard problems in an elegant way. Read the article for a full explanation and download the workbook to follow along. There are a few useful tricks along the way.

Note: This example requires Excel 365.

Excel formulas

We maintain a list of over 1000 working formulas here.

If you need more structure, we also offer video training.

Have a great weekend!

Dave

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