Question

我有1545个工作站的纬度，我想从文件中提取每个工作站的数据。我可以提取一个特定的位置，但是我不知道如何一次提取许多电台并将其存储在单独的.csv文件中。

以下代码仅适用于一个电台：

    ls()
    rm(list = ls())
    library(ncdf4)
    library(raster)
    library(rgdal)

    setwd("D:/HAII Data/Soil moisture comparison/ncfile")
    SWI <- nc_open('SWI_20170101_to_20171231.nc')
    print(SWI)
    metadata <- capture.output(print(SWI))


    lon <- ncvar_get(SWI,"lon")
    lat <- ncvar_get(SWI, "lat")
    time <- ncvar_get(SWI, "time")
    start.date = as.Date('1970-01-01')
    times.sec <- ncvar_get(SWI, 'time')
    times.day <- times.sec/(24*3600)
    datex <- start.date + times.day
    print(datex)
    time = datex
    swi.array <- ncvar_get(SWI, "SWI10_SWI_100") # store the data in a 3-                                
    dimensional array
    dim(swi.array) 
    fillvalue <- ncatt_get(SWI, "SWI10_SWI_100", "_FillValue")
    fillvalue
    nc_close(SWI)
    r_brick <- brick(swi.array, xmn=min(lat), xmx=max(lat), ymn=min(lon),                               
    ymx=max(lon), crs=CRS("+proj=longlat +ellps=WGS84 +datum=WGS84 
    +no_defs+ towgs84=0,0,0"))
    r_brick <- flip(t(r_brick), direction='y')
    toolik_lon <- 102.0028191
    toolik_lat <- 17.47608337
    toolik_series <- extract(r_brick,                 
    SpatialPoints(cbind(toolik_lon,toolik_lat)), method='bilinear')
    toolik_df <- data.frame(time, SWI=t(toolik_series))
    write.table(toolik_df, "D:/HAII Data/Soil moisture 
    comparison/data/csvfile/STN0964.csv",sep = ",")
    toolik_df

＃

1个变量（不包括尺寸变量）：浮动SWI10_SWI_100 [lon，lat，time]
_FillValue：NaN long_name：土壤水分指数单位：％

 3 dimensions:
    time  Size:36   *** is unlimited ***
        _FillValue: NaN
        units: seconds since 1970-01-01
        calendar: standard
    lat  Size:149
        _FillValue: NaN
        standard_name: latitude
        long_name: latitude
        units: degrees_north
    lon  Size:84
        _FillValue: NaN
        standard_name: longitude
        long_name: longitude
        units: degrees_east

1 global attributes:
    Conventions: CF-1.6

Answer 1

由于我没有示例日志，所以一切都是guess测的：

library(ncdf4)
library(raster)
library(rgdal)

files <- list.files(pattern = "\\.nc$") #list all nc files
length.files <- length(files)

station <- function(SWI){
  #all routine will be here:

  print(SWI)
  metadata <- capture.output(print(SWI))


  lon <- ncvar_get(SWI,"lon")
  lat <- ncvar_get(SWI, "lat")
  time <- ncvar_get(SWI, "time")
  start.date = as.Date('1970-01-01')
  times.sec <- ncvar_get(SWI, 'time')
  times.day <- times.sec/(24*3600)
  datex <- start.date + times.day
  #print(datex)
  time = datex
  swi.array <- ncvar_get(SWI, "SWI10_SWI_100") # store the data in a 3-dimensional array
  #dim(swi.array)
  fillvalue <- ncatt_get(SWI, "SWI10_SWI_100", "_FillValue")
  #fillvalue
  r_brick <- brick(swi.array, xmn=min(lat), xmx=max(lat), ymn=min(lon),                               
                   ymx=max(lon), crs=CRS("+proj=longlat +ellps=WGS84 +datum=WGS84 
                                         +no_defs+ towgs84=0,0,0"))
  r_brick <- flip(t(r_brick), direction='y')
  toolik_lon <- 102.0028191 #is this a constant? if not take it out and made it as arg on for-loop
  toolik_lat <- 17.47608337
  toolik_series <- extract(r_brick,                 
                           SpatialPoints(cbind(toolik_lon,toolik_lat)), method='bilinear')
  toolik_df <- data.frame(time, SWI=t(toolik_series))
  #write.table(toolik_df, "D:/HAII Data/Soil moisture comparison/data/csvfile/STN0964.csv",sep = ",")
  #toolik_df #commented out unless you need to see it?

  return(toolik_df)
}


#using for-loop to see inner workings
output.list <- list()
for(i in seq(from=1, to=length.files, by=1)){

  file <- files[i]

  input.swi <- nc_open(file)

  output <- station(input.swi)
  #output.list[[i]] <- output #uncomment if you want to save it into list
  write.table(output, paste0(i, ".csv", sep = ",")

  nc_close(input.swi)
}

Answer 2

天哪，您陷入了很多麻烦。比这容易得多。

library(ncdf4)
library(raster)

SWI <- brick("D:/HAII Data/Soil moisture comparison/ncfile/SWI_20170101_to_20171231.nc")

#example points
lon <- c(102, 103)
lat <- c(17, 18)
lonlat <- cbind(lon, lat)

toolik_series <- extract(SWI, lonlat, method='bilinear')

从R中的nc文件中提取多个工作站数据并写入csv文件

2 个答案: