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Exercise

Custom aggregation periods

Find the median number of Evanston 311 requests per day in each six month period from 2016-01-01 to 2018-06-30. Build the query following the three steps below.

Recall that to aggregate data by non-standard date/time intervals, such as six months, you can use generate_series() to create bins with lower and upper bounds of time, and then summarize observations that fall in each bin.

Remember: you can access the slides with an example of this type of query using the PDF icon link in the upper right corner of the screen.

Instructions 1/3
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  • Use generate_series() to create bins of 6 month intervals. Recall that the upper bin values are exclusive, so the values need to be one day greater than the last day to be included in the bin.

    • Notice how in the sample code, the first bin value of the upper bound is July 1st, and not June 30th.
    • Use the same approach when creating the last bin values of the lower and upper bounds (i.e. for 2018).
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