FILTERING

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Three-way relationships can be explored by looking at the relationship between two of them for different ranges of values of the third. Consider the relationship between cloud and temperature for different times of the day.

First categorise the time periods into day (7am to 6pm) and night (7pm to 6am). Since the times are recorded as a 24 hour clock this translates to 0-6 (night), 7-18 (day), 19-23 (night).
Highlight the weather data and select Data > Filter > Autofilter. You will then get drop-down arrows directly on the column labels of the list as shown on the right for column B (hour).

Click on the arrow beside hour and a list of the distinct items in that column will appear. On selection of any one of them only those rows matching the constraint will appear.
By choosing (Custom...) the dialogue box shown on the right appears (adjusted here to select the night time values). Use the down arrows to change from equals to less than or equals to, and similarly for is greater than or equal to. Remember to change And to Or between the two conditions.

After splitting the 24 hour data into night and day, plot cloud against temp for both periods separately as below:

night           day
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Basic statistics in Excel   23.2.99   Page: 14 of 25