[英]Subset R rasterstack based on difference in raster layers grid cell numbers
当上一层和下一层之间的差异都是NA
时,我想创建光栅堆栈的子集并将它们写为新堆栈。 即,从第 1 层开始,我想创建光栅堆栈的子集,直到前一层和下一层之间没有重叠像素(即,两层之间的差异都是NA
)所以我想要的是; 从第 1 层开始,保留前一层和下一层之间至少有 1 个公共像素的所有层,将它们写为 1 堆栈,然后移动到下一层。 以下是示例数据和不成功的 for 循环。 在这个例子中,我想保留 1:8 层,命名并编写它们,然后从第 9 层重新开始,依此类推。
r <- raster(ncol=5, nrow=5)
set.seed(0)
#create raster layers with some values
s <- stack(lapply(1:8, function(i) setValues(r, runif(ncell(r)))))
s1<-extend(s,c(-500,100,-400,100))
#to recreate the condition I am looking for, create 2 layers with `NA` vlaues
s2 <- stack(lapply(1:2, function(i) setValues(r, runif(ncell(r)))))
s1e<-extend(s2,c(-500,100,-400,100))
s1e[]<-NA
#Stack the layers
r_stk<-stack(s1,s1e)
plot(r_stk)
#here is the sample code showing what i am expecting here but could not get
required_rst_lst<-list() # sample list of raster layers with overlapping pixels I am hoping to create
for ( i in 1: nlayers(r_stk))
# i<-1
lr1<-subset(r_stk,i)
lr1
lr2<-subset(r_stk,i+1)
lr2
diff_lr<-lr1-lr2
plot(diff_lr)
if ((sum(!is.na(getValues(diff_lr)))) ==0)) #??
required_rst_lst[[i]] #?? I want layers 1: 8 in this list
#because the difference in these layers in not NA
像这样的东西可能对你有用。
您的示例数据
library(raster)
r <- raster(ncol=5, nrow=5)
set.seed(0)
s <- stack(lapply(1:8, function(i) setValues(r, runif(ncell(r)))))
s1 <- extend(s,c(-500,100,-400,100))
s2 <- stack(lapply(1:2, function(i) setValues(r, runif(ncell(r)))))
s1e <- extend(s2,c(-500,100,-400,100))
values(s1e) <- NA
r_stk <- stack(s1,s1e)
解决方案:
out <- lst <- list()
nc <- ncell(r_stk)
for (i in 1:nlayers(r_stk)) {
if (i==1) {
j <- 1
s <- r_stk[[i]]
} else {
s <- s + r_stk[[i]]
}
if (freq(s, value=NA) == nc) {
ii <- max(j, i-1)
out <- c(out, r_stk[[j:ii]])
s <- r_stk[[i]]
j <- i
}
}
out <- c(out, r_stk[[j:i]])
out
#[[1]]
#class : RasterStack
#dimensions : 14, 9, 126, 8 (nrow, ncol, ncell, nlayers)
#resolution : 72, 36 (x, y)
#extent : -468, 180, -414, 90 (xmin, xmax, ymin, ymax)
#crs : +proj=longlat +datum=WGS84 +no_defs
#names : layer.1.1, layer.2.1, layer.3, layer.4, layer.5, layer.6, layer.7, layer.8
#min values : 0.06178627, 0.01339033, 0.07067905, 0.05893438, 0.01307758, 0.03554058, 0.06380848, 0.10087313
#max values : 0.9919061, 0.8696908, 0.9128759, 0.9606180, 0.9926841, 0.9850952, 0.8950941, 0.9437248
#
#[[2]]
#class : RasterLayer
#dimensions : 14, 9, 126 (nrow, ncol, ncell)
#resolution : 72, 36 (x, y)
#extent : -468, 180, -414, 90 (xmin, xmax, ymin, ymax)
#crs : +proj=longlat +datum=WGS84 +no_defs
#source : memory
#names : layer.1.2
#values : NA, NA (min, max)
#
#[[3]]
#class : RasterLayer
#dimensions : 14, 9, 126 (nrow, ncol, ncell)
#resolution : 72, 36 (x, y)
#extent : -468, 180, -414, 90 (xmin, xmax, ymin, ymax)
#crs : +proj=longlat +datum=WGS84 +no_defs
#source : memory
#names : layer.2.2
#values : NA, NA (min, max)
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