TLinearFittter and NormalEq: What am I doing wrong?

ROOT
1

Hello all.

The output of the attached modification of solveLinear.C is:

<root_output>

$ root solveLinear.C
[snip]
ROOT 5.19/02 (trunk@22600, May 12 2008, 20:41:00 on linuxx8664gcc)

CINT/ROOT C/C++ Interpreter version 5.16.29, Jan 08, 2008
[snip]

    1. Normal Equations par[1] 0.635849 par[2] 1.06618
    1. SVD par[1] 0.635849 par[2] 1.06618
    1. TLinearFitter par[1] 2.85556 par[2] -0.677778

</root_output>

I would expect (3) to give exactly the same results as (1.) and (2.) (which are correct).
Obviously I did not set up correctly the TLinearFitter ctor.
What is the problem?

Many thanks,
Dimitris
solveLinear.C (1.42 KB)

2

Hi Dimitris,

In the line, where you assign the data, the second parameter to TLinearFitter::AssignData() has to be 1, not 2, as it’s the number of columns of the X matrix (which in your case is the vector ax).

In other words, it’s the number of dimensions in the fitting formula, not the number of linear terms in it. Maybe I should clarify this in the documentation.

Hope it helps
Anna[/code]

3

Case closed!

Thanks Anna.