从栅格列表计算平均值并将其保存为不同的名称

Question

我有一个多年来的光栅列表（.tif 格式）。这是来自 landsat 的 16 天 NDVI，我想制作月度 NDVI（两个连续栅格的平均值）并将其保存在与月度平均值相同或不同的目录中

我列出了栅格 rasters 并将其堆叠起来，后来我使用 stackApply 计算平均值，但它会产生空栅格。一年我有 23 张图像，我想将其平均并制作 12 个月。这就是我的光栅文件的样子

 "landsatNDVISC05SLC2000001.tif" "landsatNDVISC05SLC2000017.tif"
 "landsatNDVISC05SLC2000033.tif" "landsatNDVISC05SLC2000049.tif"
 "landsatNDVISC05SLC2000065.tif" "landsatNDVISC05SLC2000081.tif"
 "landsatNDVISC05SLC2000097.tif" "landsatNDVISC05SLC2000113.tif"
 "landsatNDVISC05SLC2000129.tif" "landsatNDVISC05SLC2000145.tif"
 "landsatNDVISC05SLC2000161.tif" "landsatNDVISC05SLC2000177.tif"
 "landsatNDVISC05SLC2000193.tif" "landsatNDVISC05SLC2000209.tif"
 "landsatNDVISC05SLC2000225.tif" "landsatNDVISC05SLC2000241.tif"
 "landsatNDVISC05SLC2000257.tif" "landsatNDVISC05SLC2000273.tif"
 "landsatNDVISC05SLC2000289.tif" "landsatNDVISC05SLC2000305.tif"
 "landsatNDVISC05SLC2000321.tif" "landsatNDVISC05SLC2000337.tif"
 "landsatNDVISC05SLC2000353.tif

此代码有效，但会产生超过 12 个空栅格，我还想将栅格块保存为单个子集月栅格

library(raster)
lrast<-list.files("G:/LANDSAT-NDVI/testAverage")
layers<-paste("landsatNDVISC05SLC2000", seq(from=001, to=353,by=16))
stak<-stack(lrast)
raster<-stackApply(stak, layers, fun = mean)

我想将 landsatNDVISC05SLC2000001.tif 和 landsatNDVISC05SLC2000017.tif 的月平均值设为 landsatNDVISC05SLC2000M1.tif。同样，33,49，因为我只有 23 个光栅，所以我想将 landsatNDVISC05SLC2000353.tif 保留为 landsatNDVISC05SLC2000M12.tif

Blockquote

Answer 1

不确定 stackapply 是如何工作的，但像这样的东西应该可以完成所需的工作。

library(raster)
files <- list.files(path = "...", full.names = T, pattern = ".tif")

stk <- stack()

for (i in files){
  print(i)
  as <- raster(files[i])
  stk <- addLayer(stk, as)
}

jday <-c("landsatNDVISC05SLC2000017.tif","landsatNDVISC05SLC2000033.tif",
"landsatNDVISC05SLC2000049.tif","landsatNDVISC05SLC2000065.tif","landsatNDVISC05SLC2000081.tif",
"landsatNDVISC05SLC2000097.tif","landsatNDVISC05SLC2000113.tif","landsatNDVISC05SLC2000129.tif",
"landsatNDVISC05SLC2000145.tif","landsatNDVISC05SLC2000161.tif","landsatNDVISC05SLC2000177.tif",
"landsatNDVISC05SLC2000193.tif","landsatNDVISC05SLC2000209.tif","landsatNDVISC05SLC2000225.tif",
"landsatNDVISC05SLC2000241.tif","landsatNDVISC05SLC2000257.tif","landsatNDVISC05SLC2000273.tif",
"landsatNDVISC05SLC2000289.tif","landsatNDVISC05SLC2000305.tif","landsatNDVISC05SLC2000321.tif",
"landsatNDVISC05SLC2000337.tif","landsatNDVISC05SLC2000353.tif")

jday <- as.numeric(substr(jday, 24, 25)) #substract the julien days (which I think these number represent before .tif; or you can substract the names from the 'files' vector)

dates <- as.Date(jday, origin=as.Date("2000-01-01")) # create a Date vector

stk <- setZ(stk, dates) # assign the date vector to the raster stack

raster <- zApply(stk, by = format(dates,"%Y-%m"), fun = mean, na.rm = T) # create the monthly stack

从栅格列表计算平均值并将其保存为不同的名称

calculate mean from list of rasters and and save it in a different name

r

raster