CODEWITHSUNDEEP
rgeospatialspatial
tnt
tnt

Reputation: 1459

calculating centroid of raster

I have a list (s) containing information on the probable locations of many animals in South America. For example, this is the type of stored information and what it looks like when plotted for the first individual.

Example: 

> s[1]
[[1]]
class       : RasterLayer 
dimensions  : 418, 313, 130834  (nrow, ncol, ncell)
resolution  : 0.16666, 0.16666  (x, y)
extent      : -86.333, -34.16842, -55.91633, 13.74755  (xmin, xmax, ymin, ymax)
coord. ref. : NA 
data source : in memory
names       : layer 
values      : 0, 1  (min, max)
> plot(s[[1]])

enter image description here

Note: the green areas are all "likely" locations and the grey areas are "unlikely" locations.

I would like to calculate the centroid of this probable location (i.e., centroid of the green area).

Below @dww suggested the following solution (which works for the simulated data), but leads to an error message with my data.

colMeans(xyFromCell(s, which(s[]==1)))

Error in xyFromCell(s[1], which(s[] == 1)) : 
trying to get slot "extent" from an object of a basic class ("list") with no slots

Upvotes: 4

Views: 3615

Answers (1)

dww
dww

Reputation: 31452

To find the centroid of the cells where a raster r has the value 1, you can use

colMeans(xyFromCell(r, which(r[]==1)))

Essentially, the centroid is at the mean of the latitudes/longitudes of the subsetted locations.

Here's some reproducible dummy data to test on:

r = raster(matrix(sample(0:1, 10000,T), nrow=100,ncol=100))

Upvotes: 6

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