r - terra::distance 仅报告到 NA 栅格像元的距离

Question

我正在尝试使用terra::distance我会使用raster::distanceFromPoints的 . 但是，terra::distance仅报告从点到 NA 单元的距离。这是预期的结果吗？我在我的解决方法中包含了示例代码。

带点的栅格图用于距离计算

terra::distance 的点图

期望的输出

r <- terra::rast(ncols=10, nrows=10)
valR <- rep(1, length = 100)
valR[c(1,12,23,34,45,56,67,78,89,100)] <- NA
terra::values(r) <- valR

xp <- c(50)
yp <- c(50)
xyp <- cbind(xp, yp)
vecP <- terra::vect(xyp)

terra::plot(r)
terra::plot(vecP, add=T)

rDist <- terra::distance(r, vecP)
terra::plot(rDist) #only NA cells have the distance value

# WORKAROUND
r1 = r*0
r1[is.na(r1)] <- 100
r1[r1<1] <- NA
r1Dist <- terra::distance(r1, vecP)
terra::plot(r1Dist)

####################
# using raster::distanceFromPoints
####################

rR <- raster::raster(ncols=10, nrows=10)
raster::values(rR) <- valR
raster::plot(rR)

rRDist <- raster::distanceFromPoints(rR, xyp)
rRDist <- raster::mask(rRDist, rR)
raster::plot(rRDist)

Answer 1

I tested this using distance to a SpatVector of lines rather than points. That seems to work as expected. I assume that maybe it has not been implemented for points yet.

So, another workaround you could use is to calculate distance to lines of zero length (which are basically equivalent to points):

x1 <- rbind(c(50,50), c(50,50))
colnames(x1) <- c('x', 'y')
lns <- vect(x1, "lines")

rDist <- distance(r, lns)
plot(rDist)