[R] Scaling Matrix in qda() function in MASS package

[Bert Gunter]

You need to learn how to access code for nonexported methods.  See ? "::"

> methods(qda)
[1] qda.data.frame* qda.default*    qda.formula*    qda.matrix*
see '?methods' for accessing help and source code

Shows you that the methods are not exported from the namespace. Hence
you need to use the triple colon operator to see their code:

> MASS:::qda

Once you have the code, I presume this will answer your question.

Cheers,
Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Wed, Aug 23, 2017 at 2:44 PM, Souradeep Chattapadhyay
<soura at iastate.edu> wrote:
> Hello,
>            I am Souradeep Chattopadhyay and I am a graduate student at Iowa
> State University Department of Statistics.
>
> Can anyone please explain the mathematical formulation behind the scaling
> matrix returned by the qda function in MASS package. I want to understand
> how this scaling matrix is derived from the inputs given to the qda
> function.
>
> Example Code
>
> The following example is using the banknote data in the MCLUST package.
>
> *Code*
>
> require(MASS)
> require(mclust)
> data(banknote)
> quad<-qda(banknote[,-1], grouping=banknote$Status, method="mle")
> quad$scaling
>
>
> Scaling matrix returned by qda for this data is
>
> , , counterfeit
>
>                 1                    2              3
>  4                     5          6
> Length   2.853988  1.069414 -0.05279774  0.750531723 -0.2053821  0.6986088
> Left        0.000000 -4.208108 -3.04707132 -0.026804815 -0.8644062
> -1.1088947
> Right      0.000000  0.000000  4.27383763  0.003205759  0.3313675  1.3865888
> Bottom   0.000000  0.000000  0.00000000  0.917596063 -0.8707772  0.7274894
> Top         0.000000  0.000000  0.00000000  0.000000000 -2.2041415
>  0.6956074
> Diagonal 0.000000  0.000000  0.00000000  0.000000000  0.0000000-2.1879157
>
> , , genuine
>
>                 1                     2               3                4
>               5               6
> Length  2.592911 -1.169164  0.6105339 -0.3614352 -0.2520496 -0.5281743
> Left       0.000000  3.027882  2.2392994 -0.2842368 -1.2092325  0.6927868
> Right    0.000000  0.000000 -3.8684746 -0.3972362 -0.4177546 -0.1062555
> Bottom 0.000000  0.000000  0.0000000  1.6376150  1.7274240  0.3969998
> Top       0.000000  0.000000  0.0000000  0.0000000  2.3022115  0.6318543
> Diagonal 0.000000  0.000000  0.0000000  0.0000000  0.0000000  2.4516680
>
>
>
> Thanks and Regards
>
> Souradeep
>
>         [[alternative HTML version deleted]]
>
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