python - 如何获得具有特定维度的 netCDF 变量列表？

Question

{
dimensions:
    grp = 50 ;
    time = UNLIMITED ; // (0 currently)
    depth = 3 ;
    scalar = 1 ;
    spectral_bands = 2 ;
    x1AndTime = 13041 ;
    x2AndTime = 13041 ;
    midTotoAndTime = 13041 ;
variables:
    double time(time) ;
    double a1(time, hru) ;
    double a2(time, hru) ;
    double a3(x1AndTime, hru) ;
    double a4(x2AndTime, hru) ;
    double a5(hru) ;

打开 netCDF 文件R

out <- ncdf4::nc_open('test.nc')

获取所有变量

ncvars <- names(out[['var']])

这为我提供了 netCDF 文件中所有变量的列表。

例如，如何获取具有维度time和的变量列表hru？

预期输出：

列出与a1, a2

Answer 1

注意：这是 python，而不是 R，但说明了逻辑。

import netCDF4

out = netCDF4.Dataset("test.nc")
# list of vars w dimenions 'time' and 'hru'
wanted_vars = []

# loop thru all the variables
for v in out.variables:
  # this is the name of the variable.
  print v
  # variable.dimensions is a tuple of the dimension names for the variable
  # In R you might need just ('time', 'hru')
  if out.variables[v].dimensions == (u'time', u'hru'):
    wanted_vars.append(v)

print wanted_vars

Answer 2

nc <- ncdf4::nc_open("/some/nc/file.nc")
for (vi in seq_along(nc$var)) { # for all vars of nc file
   dimnames_of_var <- sapply(nc$var[[vi]]$dim, "[[", "name")
   message(length(nc$var[[vi]]$dim), " dims of var ", names(nc$var)[vi], ": ", 
        paste(dimnames_of_var, collapse=", "))
   if (all(!is.na(match(dimnames_of_var, c("hru", "time"))))) { # order doesnt matter
      message("variable ", names(nc$var)[vi], " has the wanted dims!")
   }
}