使用 xarray open_mfdataset 函数时出错

Question

我正在尝试合并多个具有相同维度的 netCDF 文件，它们的维度如下：

OrderedDict([(u'lat', <type 'netCDF4._netCDF4.Dimension'>: name = 'lat', size = 720
), (u'lon', <type 'netCDF4._netCDF4.Dimension'>: name = 'lon', size = 1440
), (u'time', <type 'netCDF4._netCDF4.Dimension'>: name = 'time', size = 96
), (u'nv', <type 'netCDF4._netCDF4.Dimension'>: name = 'nv', size = 2
)])
OrderedDict([(u'lat', <type 'netCDF4._netCDF4.Dimension'>: name = 'lat', size = 720
), (u'lon', <type 'netCDF4._netCDF4.Dimension'>: name = 'lon', size = 1440
), (u'time', <type 'netCDF4._netCDF4.Dimension'>: name = 'time', size = 96
), (u'nv', <type 'netCDF4._netCDF4.Dimension'>: name = 'nv', size = 2
)])
OrderedDict([(u'lat', <type 'netCDF4._netCDF4.Dimension'>: name = 'lat', size = 720
), (u'lon', <type 'netCDF4._netCDF4.Dimension'>: name = 'lon', size = 1440
), (u'time', <type 'netCDF4._netCDF4.Dimension'>: name = 'time', size = 96
), (u'nv', <type 'netCDF4._netCDF4.Dimension'>: name = 'nv', size = 2
)])
OrderedDict([(u'lat', <type 'netCDF4._netCDF4.Dimension'>: name = 'lat', size = 720
), (u'lon', <type 'netCDF4._netCDF4.Dimension'>: name = 'lon', size = 1440
), (u'time', <type 'netCDF4._netCDF4.Dimension'>: name = 'time', size = 96
), (u'nv', <type 'netCDF4._netCDF4.Dimension'>: name = 'nv', size = 2
)])
OrderedDict([(u'lat', <type 'netCDF4._netCDF4.Dimension'>: name = 'lat', size = 720
), (u'lon', <type 'netCDF4._netCDF4.Dimension'>: name = 'lon', size = 1440
), (u'time', <type 'netCDF4._netCDF4.Dimension'>: name = 'time', size = 96
), (u'nv', <type 'netCDF4._netCDF4.Dimension'>: name = 'nv', size = 2
)])
OrderedDict([(u'lat', <type 'netCDF4._netCDF4.Dimension'>: name = 'lat', size = 720
), (u'lon', <type 'netCDF4._netCDF4.Dimension'>: name = 'lon', size = 1440
), (u'time', <type 'netCDF4._netCDF4.Dimension'>: name = 'time', size = 96
), (u'nv', <type 'netCDF4._netCDF4.Dimension'>: name = 'nv', size = 2
)])
OrderedDict([(u'lat', <type 'netCDF4._netCDF4.Dimension'>: name = 'lat', size = 720
), (u'lon', <type 'netCDF4._netCDF4.Dimension'>: name = 'lon', size = 1440
), (u'time', <type 'netCDF4._netCDF4.Dimension'>: name = 'time', size = 96
), (u'nv', <type 'netCDF4._netCDF4.Dimension'>: name = 'nv', size = 2
)])

但是，在使用 open_mfdataset 时，我得到了这个错误：

xr.open_mfdataset(path_file, decode_times=False)

*** ValueError: cannot infer dimension to concatenate: supply the ``concat_dim`` argument explicitly

如何解决这个错误？我的尺寸在所有文件中都相同

Answer 1

http://xarray.pydata.org/en/stable/generated/xarray.open_mfdataset.html

xarray.open_mfdataset(paths, chunks=None, concat_dim=None, preprocess=None, engine=None, lock=None, **kwargs)

看来需要你给一个concat_dim参数。从您的数据推断它时遇到问题。

Dimension to concatenate files along. This argument is passed on to xarray.auto_combine() along with the dataset objects. You only need to provide this argument if the dimension along which you want to concatenate is not a dimension in the original datasets, e.g., if you want to stack a collection of 2D arrays along a third dimension.

这些 3d 数组是否要沿新的第 4 维度堆叠？

Answer 2

出现此错误消息的原因可能是您有两个具有相同变量和坐标值的文件，而 xarray 不知道是否应该将它们沿新的维度堆叠在一起，或者只是检查以确保 none 的价值观冲突。

如果用 concat_dim=None 显式调用 open_mfdataset 会禁用所有连接尝试，那就太好了。 This change 应该将其纳入下一个 xarray 版本 (v0.9.0)。

同时，您可以通过单独打开文件并显式合并它们来解决此问题，例如，

def open_mfdataset_merge_only(paths, **kwargs):
    if isinstance(paths, basestring):
        paths = sorted(glob(paths))
    return xr.merge([xr.open_dataset(path, **kwargs) for path in paths])

在幕后，这基本上就是 open_mfdataset 所做的一切。

使用 xarray open_mfdataset 函数时出错

Error on using xarray open_mfdataset function

python

numpy

netcdf

python-xarray

netcdf4