CODEWITHSUNDEEP
rstatisticsgeospatialrasterr-raster
vineet
vineet

Reputation: 13

Retreiving output raster comparing two rater layer in R

I have two raster layer of dimension (7801, 7651). I want to compare each pixel of one raster layer with the other and create a new raster which has the minimum pixel value among the initial two raster. That is, if any i,j pixel of raster 1 has value 25 and same i,j pixel of raster 2 has value 20, thus in the output raster the i,j pixel should be 20.

Upvotes: 1

Views: 1142

Answers (2)

aldo_tapia
aldo_tapia

Reputation: 1228

Using @loki's example, you have three more options to calculate minimum value for both layers:

library(raster)

calc(stack(r1,r2),fun=min,na.rm=T)

stackApply(stack(r1,r2),indices = c(1,1),fun='min',na.rm=T)

overlay(r1,r2,fun=min,na.rm=T)

Upvotes: 1

loki
loki

Reputation: 10350

You can just use min with two raster layers.
Let's start with a reproducible example:

library(raster)
r1 <- raster(ncol = 5, nrow = 5)
r1[] <- 1:ncell(r1)
plot(r1)
r2 <- raster(ncol = 5, nrow = 5)
r2[] <- ncell(r2):1
par(mfrow = c(1,3))
plot(r1)
plot(r2)

Now we calculate the min of each overlapping cell within the two raster layers very easily with the implemented cell statistics: 

r3 <- min(r2, r1)

plot(r3)

plot with all rasters

Furthermore, you can also apply statistics like mean, max, etc.

If the implemented statistics somehow fail, or you want to use your own statistics, you can also directly access the data per pixel. That is, you first copy one of the raster layers. 

r3 <- r1

Afterwards, you can apply a function over the values. 

r3[] <- apply(cbind(r1[], r2[]), 1, min)

Upvotes: 1

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