Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-12 Thread Nikos Alexandris
On Monday 09 of December 2013 14:29:21 you wrote: Great! So, applied the diff. Here some numbers: PC1 238310.68 ( 0.1606, 0.2231, 0.1228, 0.9536) [96.10%] PC2 9364.65 ( 0.4319, 0.5989, 0.6082,-0.2912) [ 3.78%] PC3217.78 ( 0.7028, 0.1609,-0.6897,-0.0672) [ 0.09%] PC4 80.33 (

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-09 Thread Moritz Lennert
On 07/12/13 17:46, Nikos Alexandris wrote: Moritz Lennert wrote: .. Try the attached diff to imagery/i.pca/main.c. Great! So, applied the diff. Here some numbers: PC1 238310.68 ( 0.1606, 0.2231, 0.1228, 0.9536) [96.10%] PC2 9364.65 ( 0.4319, 0.5989, 0.6082,-0.2912) [ 3.78%] PC3217.78 (

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-08 Thread Markus Metz
On Thu, Dec 5, 2013 at 1:15 PM, Nikos Alexandris n...@nikosalexandris.net wrote: Nikos Alexandris: ...we need those extra digits to make it easy rejecting last Principal Component(s) prior to the backward PCA. Might be one, two or numerous (?) depending on the dimensions. Markus M: I

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-05 Thread Moritz Lennert
On 04/12/13 23:46, Nikos Alexandris wrote: Nikos Alexandris: Here, immediate effect when percent=99.68. I guess it gets rounded to 99.7 ? Moritz Lennert: Actually, the man page says percent=integer. The input is treated with atoi(). I don't know if that rounds or floors.. Heck, overlooked

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-05 Thread Markus Metz
On Wed, Dec 4, 2013 at 3:42 PM, Nikos Alexandris n...@nikosalexandris.net wrote: Nikos Alexandris wrote: 1) I can't see any differences in the derived Principal Components .. okay, to clarify: I mean the resulting images which, initially are Principal Components (synthetic images) and,

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-05 Thread Nikos Alexandris
Nikos A: Sorry for the noise. Then I need to see why the rescaling is not getting at [0,255]. Markus M: Rescaling applies to PC scores. With filtering, the output is not PC scores, but a filtered version of the input. If you want the filtered output to be rescaled, please use r.recode

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-05 Thread Nikos Alexandris
Nikos Alexandris: ...we need those extra digits to make it easy rejecting last Principal Component(s) prior to the backward PCA. Might be one, two or numerous (?) depending on the dimensions. Markus M: I think it rather depends in the amount of information encoded in each PC. It does. PCA

[GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-04 Thread Nikos Alexandris
Hi list and Markus. The i.pca module in G7 offers a forward/filtering/backward PCA. I have an issue first with filtering and second with rescaling. 1) I can't see any differences in the derived Principal Components between percent=70 and percent=99 for 4 bands which the PCs (both centered

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-04 Thread Moritz Lennert
On 04/12/13 14:53, Nikos Alexandris wrote: Hi list and Markus. The i.pca module in G7 offers a forward/filtering/backward PCA. I have an issue first with filtering and second with rescaling. 1) I can't see any differences in the derived Principal Components between percent=70 and percent=99

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-04 Thread Nikos Alexandris
On Wednesday 04 of December 2013 16:22:51 Nikos Alexandris wrote: Nikos Alexandris wrote: The i.pca module in G7 offers a forward/filtering/backward PCA. I have an issue first with filtering and second with rescaling. 1) I can't see any differences in the derived Principal

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-04 Thread Moritz Lennert
On 04/12/13 15:22, Nikos Alexandris wrote: Nikos Alexandris wrote: The i.pca module in G7 offers a forward/filtering/backward PCA. I have an issue first with filtering and second with rescaling. 1) I can't see any differences in the derived Principal Components okay, to clarify: I mean

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-04 Thread Moritz Lennert
On 04/12/13 15:34, Nikos Alexandris wrote: On Wednesday 04 of December 2013 16:22:51 Nikos Alexandris wrote: Nikos Alexandris wrote: The i.pca module in G7 offers a forward/filtering/backward PCA. I have an issue first with filtering and second with rescaling. 1) I can't see any differences

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-04 Thread Nikos Alexandris
Moritz Lennert wrote: Which components are used ? IIUC, in both cases it will be PCs 1 and 2 as PC1 70% and PC1 + PC2 90% Absolutely true (see previous post, I didn't cc you :(). Yet, consider the following cases (just to justify why I started this thread): 1) Centered and Scaled with:

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-04 Thread Moritz Lennert
On 04/12/13 16:18, Nikos Alexandris wrote: Here, immediate effect when percent=99.68. I guess it gets rounded to 99.7 ? Actually, the man page says percent=integer. The input is treated with atoi(). I don't know if that rounds or floors.. Moritz

Re: [GRASS-dev] PCA (i.pca) in G7: filtering and rescaling

2013-12-04 Thread Nikos Alexandris
Nikos Alexandris: Here, immediate effect when percent=99.68. I guess it gets rounded to 99.7 ? Moritz Lennert: Actually, the man page says percent=integer. The input is treated with atoi(). I don't know if that rounds or floors.. Heck, overlooked that :-(. In my very humble and