The Reduce Plugin performs calculations appearing on other pages while collecting results into a summary. A slider allows one to vary one or more parameters while viewing the impact these have on the outcomes.
FOLD Included Pages WATCH Bottles of Beer SLIDE Bottles of Beer
See the Beer Drinking Scenarios example.
Find source on GitHub 
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Configuration
Double click the summary to edit its configuration. The plugin interprets these words.
WATCH variable name to see the variable's value at the end of each page of methods.
SLIDE variable name to scrub through values from 0 to 2x the variable's previous value. Scrub through 0 to 100 if no previous value.
FOLD page fold name to select a fold containing links to pages with calculations. One can drag links into or out of this fold to alter the choice and order of pages summarized.
Included Pages
End of Included Pages
Double click the slider's thumb to retrieve a spreadsheet version of the calculation. See More About Reduce Plugin.
About the Name
The term "reduce" comes from map-reduce where the second step "collects the answers to all the sub-problems and combines them in some way to form the output – the answer to the problem it was originally trying to solve." wikipedia