https://bz.apache.org/bugzilla/show_bug.cgi?id=62836
Bug ID: 62836
Summary: [PATCH] Implementation of Excel TREND function
Product: POI
Version: 4.0.x-dev
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P2
Component: SS Common
Assignee: dev@poi.apache.org
Reporter: matthi...@protonmail.com
Target Milestone: ---
Created attachment 36200
--> https://bz.apache.org/bugzilla/attachment.cgi?id=36200&action=edit
TREND patch
This is an incomplete implementation of the Excel TREND function. Most cases do
work already, but some don't work yet due to the way the math library handles
multiple linear regression. Specifically, cases where there are more x
variables than the sample size and some cases where there are duplicate x
values fail. The former seems to have been fixed since in the math library
(https://github.com/Hipparchus-Math/hipparchus/issues/13), but the fix isn't in
the currently used version yet. I'm not sure how to fix the latter because
having duplicate x values doesn't seem to make too much sense, so I'm not
entirely sure what Excel actually does.
Some of the code (especially for handling all the different shapes excel
allows) is pretty rough, but I hope it's acceptable as a first implementation.
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