https://bugs.freedesktop.org/show_bug.cgi?id=54423
Bug #: 54423
Summary: Linear regression line equation incorrect
Classification: Unclassified
Product: LibreOffice
Version: 3.6.1.2 release
Platform: x86-64 (AMD64)
OS/Version: Mac OS X (All)
Status: UNCONFIRMED
Severity: normal
Priority: medium
Component: Chart
AssignedTo: [email protected]
ReportedBy: [email protected]
Created attachment 66533
--> https://bugs.freedesktop.org/attachment.cgi?id=66533
File comparing manually calculated regressionformula and formula as shown in
graph
Problem: The equation shown along the linear regression line inside the diagram
is incorrect (the actual line drawn seems to be correct).
Formula design: f(x) = a + bx (I'll be referring to a and be later on)
Steps to reproduce
1. Create a data range with x, y values
2. Plot it along the x axis
3. Create a regression line and enable the equation
4. Test the result of the equation
Obtained result:
Although the regression line that is drawn seems to be correct, the equation
contains is not: the equation's value for b is correct, but a is incorrect.
Expected result:
The error should be relatively small (i.e. the f(x) values resulting from the
regression line should be somewhere near the actual observed value y).
The attached file demonstrates it. I've included a manually calculated
regression line that seems to correspond to the actual line drawn.
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