根据NetCDF文件中的变量弄出来翻转(The variable from a netcdf fil

我已经下载从NC文件

f=open.ncdf("file.nc")
[1] "file Lfile.nc has  2 dimensions:"
[1] "Longitude   Size: 1440"
[1] "Latitude   Size: 720"
[1] "------------------------"
[1] "file filr.nc has   8 variables:"
[1] "short ts[Latitude,Longitude]  Longname:Skin Temperature (2mm) Missval:NA"

然后我想与变量soil_moisture_c工作

A = get.var.ncdf(nc=f,varid="soil_moisture_c",verbose=TRUE)

然后我绘制与image(A) 我得到了如下图所示的地图，我甚至调换它image(t(a))但改为另一个方向，而不是它应该如何。总之，要想知道什么是错的，我用的NetCDF观众甲胄和地图被正确地绘制成你可以看到下面。

Answer 1:

正如补充@mdsumner远更好的解决办法，这里是一个办法做到这一点利用图书馆ncdf只。

library(ncdf)
f <- open.ncdf("LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040101.nc")
A <- get.var.ncdf(nf,"soil_moisture_c")

所有你需要的是找到你的尺寸，以便有一个连贯的X和Y轴。如果你看看你的netCDF对象的尺寸，在这里你所看到的：

str(f$dim)
List of 2
 $ Longitude:List of 8
  ..$ name         : chr "Longitude"
  ..$ len          : int 1440
  ..$ unlim        : logi FALSE
  ..$ id           : int 1
  ..$ dimvarid     : num 2
  ..$ units        : chr "degrees_east"
  ..$ vals         : num [1:1440(1d)] -180 -180 -179 -179 -179 ...
  ..$ create_dimvar: logi TRUE
  ..- attr(*, "class")= chr "dim.ncdf"
 $ Latitude :List of 8
  ..$ name         : chr "Latitude"
  ..$ len          : int 720
  ..$ unlim        : logi FALSE
  ..$ id           : int 2
  ..$ dimvarid     : num 1
  ..$ units        : chr "degrees_north"
  ..$ vals         : num [1:720(1d)] 89.9 89.6 89.4 89.1 88.9 ...
  ..$ create_dimvar: logi TRUE
  ..- attr(*, "class")= chr "dim.ncdf"

因此，你的尺寸为：

 f$dim$Longitude$vals -> Longitude
 f$dim$Latitude$vals -> Latitude

现在，您Latitude 90反潜至-90相反，后者的image更喜欢，所以：

 Latitude <- rev(Latitude)
 A <- A[nrow(A):1,]

最后，你发现，你的对象A的X和Y翻转，所以你需要转它，你的NA值表示由值某些原因-32767 ：

A[A==-32767] <- NA
A <- t(A)

最后的情节：

image(Longitude, Latitude, A)
library(maptools)
data(wrld_simpl)
plot(wrld_simpl, add = TRUE)

编辑：要做到这一点在你31页的文件，让我们打电话给你的文件名的矢量ncfiles和yourpath您保存它们的目录（为简单起见我要去假设你的变量总是叫soil_moisture_c和您的NAS总是-32767 ）：

ncfiles
 [1] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040101.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040102.nc"
 [3] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040103.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040104.nc"
 [5] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040105.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040106.nc"
 [7] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040107.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040108.nc"
 [9] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040109.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040110.nc"
[11] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040111.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040112.nc"
[13] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040113.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040114.nc"
[15] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040115.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040116.nc"
[17] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040117.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040118.nc"
[19] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040119.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040120.nc"
[21] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040121.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040122.nc"
[23] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040123.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040124.nc"
[25] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040125.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040126.nc"
[27] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040127.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040128.nc"
[29] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040129.nc" "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040130.nc"
[31] "LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T173800Z_20040131.nc"

yourpath
 [1] "C:\\Users"

library(ncdf)
library(maptools)
data(wrld_simpl)
for(i in 1:length(ncfiles)){
    f <- open.ncdf(paste(yourpath,ncfiles[i], sep="\\"))
    A <- get.var.ncdf(f,"soil_moisture_c")
    f$dim$Longitude$vals -> Longitude
    f$dim$Latitude$vals -> Latitude
    Latitude <- rev(Latitude)
    A <- A[nrow(A):1,]
    A[A==-32767] <- NA
    A <- t(A)
    close.ncdf(f) # this is the important part
    png(paste(gsub("\\.nc","",ncfiles[i]), "\\.png", sep="")) # or any other device such as pdf, jpg...
    image(Longitude, Latitude, A)
    plot(wrld_simpl, add = TRUE)
    dev.off()
    }

Answer 2:

原因是，您所使用的的NetCDF接口是非常低的水平，并已完成所有被读出的变量没有它的任何维度信息。网格的方向实在是任意的，并且需要在特定的上下文中理解的坐标信息。

library(raster) ## requires ncdf package for this file  
d <- raster("LPRM-AMSR_E_L3_D_SOILM3_V002-20120520T185959Z_20040114.nc", varname = "soil_moisture_c")

（我用不同的文件到你的，但它应该工作一样）。

事实证明，即使栅格没有得到工作没有这个权利，但它可以很容易地纠正：

d <-  flip(t(d), direction = "x")

这换位数据和翻转围绕“X”（经度），保持地理坐标从原来的环境。

从maptools检查地图绘制起来：

plot(d)

library(maptools)
data(wrld_simpl)
plot(wrld_simpl, add = TRUE)

还有许多其他的方式通过读取文件中的维度信息来实现这一点，但是这至少是一个快捷方式做最艰难的工作适合你。

Answer 3:

你也可以简单地颠倒使用CDO命令行纬度：

cdo invertlat file.nc file_inverted.nc