在带有ncdf4的R中，打开netcdf文件，修改并保存到磁盘

Question

我正在尝试在R中修改和保存一个netcdf文件。我可以修改值，但似乎无法保存和保留修改后的值。以下是我正在做的事情：

使用ncdf4包打开文件

library(ncdf4)
nc=nc_open('RMinit_newvalues2017.nc', write=T)

重新分配丢失的值-该文件有2000个变量，大约一半需要修改丢失的值，我可以成功地做到这一点：

for (i in 1:10){
print(nc$var[[i]]$name) # use to match aaR/aaS
test=grep("_Nums", nc$var[[i]]$name) # search for Nums, skip to next
if (length(test) ==1){
next
}
test2=grep("_ResN", nc$var[[i]]$name) # search for RN
if (length(test2) == 1) {
print(nc$var[[i]]$missval) # print orginal value
print(xR$RN[which(xR$Variables==nc$var[[i]]$name)]) # print new value
nc$var[[i]]$missval=xR$RN[which(xR$Variables==nc$var[[i]]$name)] # assign new value
print(nc$var[[i]]$missval) # print assigned value
} else if (length(test2) != 1) {
print(nc$var[[i]]$missval)
print(xS$SN[which(xS$Variables==nc$var[[i]]$name)])
nc$var[[i]]$missval=xS$SN[which(xS$Variables==nc$var[[i]]$name)]
print(nc$var[[i]]$missval)
}
}

这里是带注释的输出，显示它正在更改"_ResN"one_answers"_StructN"的值：

[1] "Anchovies10_Nums" (nothing done here, next)
[1] "Anchovies10_ResN" (first replacement)
[1] 987.7794 (original value)
[1] 200.1975 (replacement value, printed after assignment)
[1] "Anchovies10_StructN" (repeat pattern...)
[1] 372.7469
[1] 75.54621
[1] "Anchovies1_Nums"
[1] "Anchovies1_ResN"
[1] 130.3665
[1] 15.67022
[1] "Anchovies1_StructN"
[1] 49.19491
[1] 5.913289
[1] "Anchovies2_Nums"
[1] "Anchovies2_ResN"
[1] 228.1891
[1] 34.30677
[1] "Anchovies2_StructN"
[1] 86.10911
[1] 12.94595
[1] "Anchovies3_Nums"

最后，我同步并关闭nc文件，它应该会将其保存到磁盘上。但这里什么也没发生。没有错误，一切似乎都很好，只是文件没有保存。我缺少什么？？？

nc_sync(nc)
nc_close(nc)

编辑：在循环中切换命令后，我能够保存文件。使用ncatt_put与使用nc$var[[i]]$missval=...分配似乎解决了问题。我还意识到我一开始编辑的值是错误的，因为我需要_Fillvalue来更改，而不是missval。这现在有效：

for (i in 1:dim(a)[1]){
test=grep("_Nums", nc$var[[i]]$name) # search for Nums, skip to next
if (length(test) ==1){
next
}
test2=grep("_ResN", nc$var[[i]]$name) # search for RN
if (length(test2) == 1) {
ncatt_put(nc,a[i,1],"_FillValue", xR$RN[which(xR$Variables==nc$var[[i]]$name)])
} else if (length(test2) != 1) {
ncatt_put(nc,a[i,1],"_FillValue", xS$SN[which(xS$Variables==nc$var[[i]]$name)])  
}
nc_sync(nc)
}
nc_sync(nc)
nc_close(nc)

Answer 1

发布我的解决方案作为参考，也许可以帮助未来的某个人。。。

我暂时解决了我的问题。仍然不确定为什么第一次尝试没有更新文件。我需要使用ncdf4::ncatt_put来编辑_FillValue的属性，并使用ncdf4::ncvar_put来添加数据。然后在循环中执行nc_sync会有所帮助。

for (i in 1:length(b)){
vv=as.numeric(b[i]) # index of ResN and StructN in entire list of nc file 'a'
testSN=grep("_StructN", a[vv,1]) # use to select SN values
testRN=grep("_ResN", a[vv,1]) # use to select RN values
if (length(testRN) ==1){
ncatt_put(nc,a[vv,1],"_FillValue", xR$RN[which(xR$Variables==a[vv,1])])
ncvar_put(nc,a[vv,1], rep(xR$RN[which(xR$Variables==a[vv,1])],150)) # replicate 5x30
} else if (length(testSN) ==1){
ncatt_put(nc,a[vv,1],"_FillValue", xS$SN[which(xS$Variables==a[vv,1])])
ncvar_put(nc,a[vv,1], rep(xS$SN[which(xS$Variables==a[vv,1])],150))
}
nc_sync(nc)
}
nc_sync(nc)
nc_close(nc)