从栅格计算器转移到 R 的条件命令 [英] Conditional command from Raster Calculator transfer to R

问题描述

到目前为止，我在 ArcGIS 的栅格计算器中使用了以下语句:

So far I used the following statement in the Raster Calculator of ArcGIS:

Con(("Land_use.rst" ==  -20), "Export.rst")

这会计算一个新的栅格，它只包含来自导出的数据，其中 Land_use 等于 -20.这正是我想要的.但我想在 R 中自动执行此操作，因为我必须多次这样做.

This calculates a new Raster which only contains the Data from Export where Land_use equals -20. That is exactly what I want. But I want to automatise this in R, as I have to do it a lot of times.

到目前为止，我得到了这样的东西:

So far I got something like this:

for (catch_dir in Dir_List) {

r1 <- raster(paste0(catch_dir, '/Export.rst'))

r2 <- raster(paste0(catch_dir,'/LAND_use.rst'))

### statement that output export_streams.rst contains the data of export.rst where LAND_use.rst equals -20.
  x <- overlay(r2, r1, fun=function(x,y){ y[x!=-20] <- 0; y})

 writeRaster(x, filename = paste0(catch_dir, "/export_streams.rst"), format="IDRISI", NAflag = 0, datatype = "FLT4S",
              overwrite=TRUE)
}

该代码执行以下操作:它生成一个包含 r1 值的栅格，其中 r2 = -20.所以这很好，但是栅格边界处也有剩余物，它们在 r2 中不等于 -20.不过，这两个栅格的范围是相同的.所以覆盖可能不适用于我的任务.除了叠加还有其他想法吗?也许一些 if(r2 == -20){ } 命令?

That code does the following: It produces a raster which contains the values of r1 where r2 = -20. So that is good, but there are also leftovers at the border of the raster which do not equal -20 in r2. The extent of the two rasters are the same though. So the overlay probably doesnt work for my task. Any other ideas than overlay? Maybe some if(r2 == -20){ } command?

推荐答案

您可以这样做:

m <- subs(r2, cbind(-20, 1))
x <- mask(r1, m)

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