# [R-sig-Geo] apply a formula by matrix

Alfredo Alessandrini alfreale74 at gmail.com
Thu Jul 7 12:32:16 CEST 2011

```Hi,

I've to apply a formula to a raster in relation to an index table
created from raster stack.

I'm trying to explain the problem:

I've three raster with same resolution, that I join in a raster
RasterStack, and from it I can obtain a table like this:

>  data <- stack(dem,aer550,aer550_type)

>  unique(as.matrix(data))
layer_1      layer_2 layer_3
[1,]       1 0.2460000000       2
[2,]       1 0.1845000000       2
[3,]       1 0.0000000001       2
[4,]       0 0.0000000001       2
[5,]       1 0.1476000000       2
[6,]       1 0.0000000001       0
[7,]       0 0.0000000001       0
.........
........

>From this table I develop a linear model that after I've to apply to
another raster that isn't in the raster stack and it has a higher
resolution.

I've to compute the function for the raster with higher resolution,
according to the coefficients of the rows, and only for specific
pixels.(layer_1 = 1 AND layer_2 = 0.246 AND layer_3 = 2) --> function
( -0.2710751  0.7981552 )

layer_1      layer_2 layer_3        coeff_model_1      coeff_model_2
1        1 0.2460000000       2 -0.2710751  0.7981552
2        1 0.1845000000       2 -1.1499351 -0.6216590
3        1 0.0000000001       2 -0.6643215  0.1993647
4        0 0.0000000001       2 -1.0418143  1.5379033
5        1 0.1476000000       2  2.3148048  0.8951158
6        1 0.0000000001       0 -0.2710751  0.7981552
7        0 0.0000000001       0 -1.1499351 -0.6216590
.......
.......