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 in the derived Principal Components
okay, to clarify: I mean the resulting images which, initially are Principal
Components (synthetic images) and, after applying filtering & backward PCA,
the resulting images approach the original data -- still they are modified.
Example (using i.pca in G7, though r.info below executed from G64):
<http://nikosalexandris.net/owncloud/public.php?service=files&t=e87b1223bf6402786ef7478690099602>
and details for
P=90) r.info -rh PC90N.1
min=171.596979136065
max=1107.42672094831
Data Source:
Data Description:
generated by i.pca
Comments:
Eigen values, (vectors), and [percent importance]:
PC1 2.78 ( 0.4947, 0.5922, 0.5743, 0.2735) [69.53%]
PC2 1.08 ( 0.5196, 0.0517,-0.0974,-0.8473) [26.99%]
PC3 0.11 ( 0.4210, 0.2486,-0.7926, 0.3644) [ 2.86%]
PC4 0.03 (-0.5551, 0.7647,-0.1805,-0.2729) [ 0.63%]
i.pca -n -f input="Blue_DNs,Green_DNs,Red_DNs,NIR_DNs" output_prefix\
="PC90N" rescale=0,0 percent=90
P=70) r.info -rh PC70N.1
min=171.596979136065
max=1107.42672094831
Data Source:
Data Description:
generated by i.pca
Comments:
Eigen values, (vectors), and [percent importance]:
PC1 2.78 ( 0.4947, 0.5922, 0.5743, 0.2735) [69.53%]
PC2 1.08 ( 0.5196, 0.0517,-0.0974,-0.8473) [26.99%]
PC3 0.11 ( 0.4210, 0.2486,-0.7926, 0.3644) [ 2.86%]
PC4 0.03 (-0.5551, 0.7647,-0.1805,-0.2729) [ 0.63%]
i.pca -n -f input="Blue_DNs,Green_DNs,Red_DNs,NIR_DNs" output_prefix\
="PC70N" rescale=0,0 percent=70
Which components are used ? IIUC, in both cases it will be PCs 1 and 2 as
PC1 < 70% and PC1 + PC2 > 90%
Moritz
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