从栅格中提取平均值期间返回的 NA

Question

我正在使用多边形 shapefile 从栅格中提取平均值。栅格和矢量的 CRS 相同，但也提取函数 returns NA 值。

library(rgdal)
library(raster)
options(stringsAsFactors = FALSE)
Shapefile <- readOGR("Fishnet_geolocated.shp",layer="Fishnet_geolocated")
plot(Shapefile)
CHM_Napi<-raster("Napi_CRS.tif")
crs(Shapefile)
crs(CHM_Napi)
Napi_extract <- raster::extract(CHM_Napi, # the raster that you wish to extract values from
                                Shapefile, # a point, or polygon spatial object
                                fun = mean, # extract the MEAN value from each plot
                                sp = TRUE) # create spatial object
class(Napi_extract)
summary(Napi_extract$Napi_CRS)

在运行这段代码之后我得到了一个结果-

> Shapefile <- readOGR("Fishnet_geolocated.shp",layer="Fishnet_geolocated")
OGR data source with driver: ESRI Shapefile 
Source: ""
with 63 features
It has 5 fields
Integer64 fields read as strings:  id 
> plot(Shapefile)
> CHM_Napi<-raster("Napi_CRS.tif")
> crs(Shapefile)
CRS arguments:
 +proj=utm +zone=36 +south +datum=WGS84 +units=m +no_defs +ellps=WGS84
+towgs84=0,0,0 
> crs(CHM_Napi)
CRS arguments:
 +proj=utm +zone=36 +south +datum=WGS84 +units=m +no_defs +ellps=WGS84
+towgs84=0,0,0 
> class(Napi_extract)
[1] "SpatialPolygonsDataFrame"
attr(,"package")
[1] "sp"
> summary(Napi_extract$Napi_CRS)
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.    NA's 
     NA      NA      NA     NaN      NA      NA      63

提取函数中是否缺少某些内容，我是否应该重新投影栅格和 shapefile。 P.S。在 QGIS 中，矢量层和栅格层重叠，但在 R 中不重叠。感谢任何有用的提示。

Answer 1

栅格中可能有 NA 值。像这样使用 na.rm=TRUE

Napi_extract <- raster::extract(CHM_Napi, 形状文件，有趣 = 卑鄙， na.rm =真， sp = 真）

从栅格中提取平均值期间返回的 NA

NAs returned during extract mean values from a raster

r

extract

raster