[GRASS-user] Factor loadings or Eigen vector?

[Gaspar Reyes Póndigo]

Hi, dear grass-users

The new dimensions (principle components) are formed from the eigen vector (1, 2, 3), not of the factor loadings (W). Therefore there is an error in the GRASS-wiki - Principal Components Analysis, the line of code error is copied below:

 ## Factor loadings (W=385.6992, -364.5920,37.4824,636.0665, etc..) ###    
###########################################################
Using the W vector, new maps can be created :

r.mapcalc 'pc.1 =  385.6992*map.1 +636.0665*map.2 + 474.2358*map.3'   r.mapcalc 'pc.2 = -364.5920*map.1 + 41.8027*map.2 + 240.4573*map.3'    r.mapcalc 'pc.3 =   37.4824*map.1 - 74.7964*map.2 +  69.8356*map.3'    	

###########################################################
 
Correct me if i'm wrong?

Thanks in advance 
                                                                                                                                
REFERENCES

1. Baronti, S., R. Carla, S. Sigismondi & L. Alparone. 1994. Principal component analysis for change detection on polarimetric multitemporal SAR data, Pp: 2152-2154 vol.2154, In: Geoscience and Remote Sensing Symposium, 1994. IGARSS '94. Surface and Atmospheric Remote Sensing: Technologies, Data Analysis and Interpretation, International.

2.Fung, T. & E. LeDrew. 1987. Application of Principal Components Analysis to Change Detection. Photogrammetric Engineering & Remote Sensing. 53(12): 1649-1658.

3. Singh, A. & A. Harrison. 1985. Standardized principal components. International Journal of Remote Sensing. 6(6): 883-896.

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Gaspar Reyes Póndigo
Universidad del Mar, Oaxaca, México
Campus Puerto-Ángel
Carretera principal Puerto Ángel Zipolite km 1.5 
C.P. 70902

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