[Kst] [Bug 224225] New: 'fit linear weighted' plugin produces different results

[freebody.kst at gmail.com]

https://bugs.kde.org/show_bug.cgi?id=224225

           Summary: 'fit linear weighted' plugin produces different
                    results
           Product: kst
           Version: unspecified
          Platform: Compiled Sources
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: general
        AssignedTo: kst at kde.org
        ReportedBy: freebody.kst at gmail.com


Version:           1.9.0_devel (using Devel)
OS:                Linux
Installed from:    Compiled sources

PROBLEM:
I tried to plot and fit the same data file using gnuplot and kst, the fit
results are different.

STEPS TO REPRODUCE:
1. create a txt file containing the following data


2  3.5  0.55
4  7.2  0.65
6  9.5  0.74
8  17.1  0.5
10  20.0  0.85
12  25.5  0.6

this is an example from the following web page
http://phobos.physics.uiowa.edu/~rlm/mathcad/linear%20fitting%20example%20with%20outlier.htm

2. construct a curve in kst
1.Data --> New Curve...
Choose X from the drop-down list for the X axis vector
Choose Y from the drop-down list for the Y axis vector
Choose DelY from the drop-down list for the +Y error bar
Check Show points in the Appearance panel
Click OK to view the curve

3. curve fitting in kst
Click anywhere on the plot 
Choose Fit --> Y in the appearing context menu
Choose Fit linear weighted(v0.1) in the drop down list of Plugin Selection
Click OK 

4. fit in gnuplot
f(x)=a*x+b
a=1
b=1
fit f(x) 'fit.dat' using 1:2:3 via a,b

RESULTS:
in kst, gradient:2.2310; intercept:-1.9601

EXPECTED RESULTS:
according to the webpage, the result of the weighted linear fit is
gradient:2.23; intercept:-1.528. gnuplot confirms the same result.

-- 
Configure bugmail: https://bugs.kde.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.