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I have a rasterlayer MeanMap and I would like to do some calculations of the raster values contained within a determinate polygon fregs. How can I calculate the mean and the median of the raster for each polygon?

> fregs
class       : SpatialPolygonsDataFrame 
features    : 86 
extent      : -117724.8, -58876.6, -124776.9, -70413.58  (xmin, xmax, ymin, ymax)
crs         : +proj=utm +zone=29 +datum=WGS84 +units=m +no_defs 
variables   : 6
names       : DICOFRE,           Freguesia,           Municipio, Distrito,          Des_Simpli, pop_res_ce 
min values  :  110501,       Ãguas Livres,           ALCOCHETE,   LISBOA,       Ãguas Livres,      11074 
max values  :  151007, Vila Franca de Xira, VILA FRANCA DE XIRA, SETÚBAL, Vila Franca de Xira,       9997 
> MeanMap
class      : RasterLayer 
dimensions : 500, 500, 250000  (nrow, ncol, ncell)
resolution : 175.4347, 145.9944  (x, y)
extent     : -118821.8, -31104.38, -139252.5, -66255.27  (xmin, xmax, ymin, ymax)
crs        : +proj=utm +zone=29 +datum=WGS84 +units=m +no_defs 
source     : memory
names      : layer 
values     : 1.967911, 34.79086  (min, max)
plot(MeanMap)
plot(fregs, add=T)

raster layer with limits overlayed

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just found out the raster::extract() function, it does what i needed.

mean_freg = extract(MeanMap, fregs, method="simple", fun=mean, sp=T)

this line of code adds a column with the results I needed to the original SpatialPolygonsDataFrame fregs

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    Oct 16 '21 at 14:31

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