[GRASS-stats] Correlation calculation

[Rebecca Bennett]

Hello all,

I am *very* new to R and am experimenting with the GRASS / R interface to look at correlation of elevation and spectral values.

Reading through the literature and mailing list, I have imported my GRASS rasters to R as a dataset looked at the summary statistics and then attempted to run a correlation analysis using cor, along the lines of the example here:


map <- readRAST6(c("lageado_10k_fisher_K_15x15", 
   "lageado_10k_fisher_K_25x25")) 
summary(map) 
cor(as(map, "data.frame")) 


and get the output:


                coombe_rev_LRM intensity_coombe          x          y
coombe_rev_LRM                1               NA         NA         NA
intensity_coombe          NA       1.00000000 -0.1525509 0.09057913
x                                NA      -0.15255095  1.0000000 0.00000000
y                                NA       0.09057913  0.0000000 1.00000000



so the correlation is running on the x and y values of the rasters not the z?

How do I begin to assess correlation in the z value of two rasters?

Many thanks for reading, (and sorry if my question seems stupid or I have missed something obvious)

Rebecca
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