[GRASS-dev] reg i.pca module

[Markus Metz]

On Fri, Feb 8, 2013 at 4:48 PM, Rashad M <mohammedrashadkm at gmail.com> wrote:
>
> Hi,
>
> On Thu, Feb 7, 2013 at 2:46 PM, Moritz Lennert
> <mlennert at club.worldonline.be> wrote:
>>
>> On 07/02/13 06:31, Rashad M wrote:
>>>
>>> Hi
>>>
>>> As mentioned in wiki does the output pixel = eigenvector * input pixel?
>>
>>
>> Yes, possibly depending on how the eigenvector is formulated. PCA is
>> "just" a linear transformation from original pixel space to PC space.
>
>
> What do you mean by depending on "how the eigenvector is formulated"?

>From the example in the manual:

The first PCA has the eigenvector

0.2824, 0.3342, 0.5092,-0.0087, 0.5264, 0.5217

Thus the output cells for PCA1 are calculated with

PCA1 = 0.2824 * (band1 - mean(band1) + 0.3342 * (band2 - mean(band2) +
... + 0.5217 * (band7 - mean(band7))

The output cells for the other PCA's are calculated accordingly.

>
> Can anyone confirm this because its blocking me

HTH,

Markus M