You'd need to adjust the latitude / longitude values passed to sel so that your ROI contains (or is nearest to) more than one gird point in latitude or longitude. I'm afraid there's not automatic way in Xarray to do that.

Hi @benbovy , As you can see, the slice option returns an empty latitude. From your explanation above, does it mean that it is not possible to select the latitude values and in some cases longitude values? I needed both the longitude and latitude values.

Hi @rogomichael,

It is expected in your example that sel with your given values and method='nearest' returns coordinates with duplicate longitude & latitude values.

The resolution of the grid is too coarse compared to your ROI, which is why the two provided values for latitude (longitude) both select the same grid point.

If you want to use sel for extracting a range over the latitude and longitude dimensions, it is better to use slices. It better illustrates that your ROI is smaller than the grid resolution:

```python ds.sel( longitude=slice(49.294, 49.376), latitude=slice(10.971, 11.087) )

<xarray.Dataset>

Dimensions: (time: 365, longitude: 1, latitude: 0)

Coordinates:

* time (time) datetime64[ns] 2019-01-01 2019-01-02 ... 2019-12-31

* longitude (longitude) float64 49.38

* latitude (latitude) float64

Data variables:

tg (time, latitude, longitude) float32 ...

```

@TomNicholas , I have reduced the code to a smaller portion. The reason I include a long piece of code is because the longitude and latitude values are read from the shape file and passed to xarray to read from year2019.nc. I previously attached the file in the issue above but you can still access it here.

https://1drv.ms/u/s!AvYOTGjStibEmGGsJwRlpoBfLvHm?e=LBLm95

I hope it is accessible.

import xarray as xr

nc_file = xr.open_mfdataset('year2019.nc') #, chunks = {'time': 10}) two_months_255 = nc_file["tg"].sel( longitude = [49.294, 49.376], latitude = [10.971, 11.087])

Hi @rogomichael, thanks for raising your issue.

Could you possibly turn your problem into a minimal reproducible example? That would make it much easier for us to help you.

You've included a lot of code, but from looking at it it seems to me that the only lines which matter are

```python nc_file = xr.open_mfdataset('year2019.nc')

nc_file["tg"].sel( longitude=[state_lon[0], state_lon[1]], latitude=[state_lat[0], state_lat[1]], method="nearest" ) ```

This suggests to me that your original file has duplicate values, as all xarray has done here is open it.

(However I still am not going to be able to reproduce this error without access to the file year2019.nc.)