R 循环问题：提取光栅堆栈（netCDF文件）每层的平均温度

我在RasterStack循环中遇到了一点小问题。我试图提取过去10年中北卡罗来纳州每个县每小时的平均温度。我能够运行一些简单的代码，并相对轻松地为每一层获取这些信息，但当我尝试循环此过程以获取光栅堆栈/块中每个时间戳的平均值时，我运气不太好！我非常感谢您的帮助或建议

library(tidyverse)
library(rgdal)
library(sp)
library(raster)
library(doParallel)
library(foreach)
library(ncdf4)
librarcy(exactextractr)

# Brick the NC File 
r<-stack("ERA_Temps.nc") 

output <- for (i in 1:length(r)) {
                    
              wgsraster <- r[[i]]
                    
              year <- str_sub(names(wgsraster), 2, 5)
              month <- str_sub(names(wgsraster), 7, 8)
              day <- str_sub(names(wgsraster), 10, 11)
              hour <- str_sub(names(wgsraster), 13, 14)
                    
              NC_Counties <- cbind(shp, exact_extract(wgsraster, shp, c('mean')))
                    
              output_df <- data.frame(County.Name = NC_Counties$NAME, GEOID = NC_Counties$GEOID, temp_mean = NC_Counties$mean, year, month, day, hour)
                    return(output_df)
                  }

Output <- output_df

我可以相当容易地获得我需要的单个层：

wgsraster <- r[[5]]
                
year <- str_sub(names(wgsraster), 2, 5)
month <- str_sub(names(wgsraster), 7, 8)
day <- str_sub(names(wgsraster), 10, 11)
hour <- str_sub(names(wgsraster), 13, 14)
                
NC_Counties <- cbind(shp, exact_extract(wgsraster, shp, c('mean')))
                
output_df <- data.frame(County.Name = NC_Counties$NAME, GEOID = NC_Counties$GEOID, temp_mean = NC_Counties$exact_extract.wgsraster..shp..c..mean...,
                                        year, month, day, hour)

output_df
     County.Name GEOID temp_mean year month day hour
1         Saluda 45081  298.3141 2018    09  14   11
2   Williamsburg 45089  300.2301 2018    09  14   11
3     Dorchester 45035  299.3716 2018    09  14   11
4       Berkeley 45015  299.7389 2018    09  14   11
5      Greenwood 45047  298.5175 2018    09  14   11

wgsraster <- r[[5]]
                
year <- str_sub(names(wgsraster), 2, 5)
month <- str_sub(names(wgsraster), 7, 8)
day <- str_sub(names(wgsraster), 10, 11)
hour <- str_sub(names(wgsraster), 13, 14)
                
NC_Counties <- cbind(shp, exact_extract(wgsraster, shp, c('mean')))
                
output_df <- data.frame(County.Name = NC_Counties$NAME, GEOID = NC_Counties$GEOID, temp_mean = NC_Counties$exact_extract.wgsraster..shp..c..mean...,
                                        year, month, day, hour)

output_df
     County.Name GEOID temp_mean year month day hour
1         Saluda 45081  298.3141 2018    09  14   11
2   Williamsburg 45089  300.2301 2018    09  14   11
3     Dorchester 45035  299.3716 2018    09  14   11
4       Berkeley 45015  299.7389 2018    09  14   11
5      Greenwood 45047  298.5175 2018    09  14   11

Error in .local(x, i, j, ...) : you must provide an index