xarray: How to get the coordinates of the maximum and minimum value over a spatial domain in xarray?

[anubhavchoudhary]

I have a netcdf file containing a surface variable over a latlon area. I want to get the coordinate (as lat, lon value) of maximum as well as minimum value of that variable over a certain area which I can define with latlon box. How to do it in xarray ?

[TomNicholas]

There might be a better way, but I think this is one way:

First mask out all the data that isn't in your lat/long box. If your latitude and longitude are 1D then you could use .sel(), otherwise use .where(). You have two conditions (one for latitude and one for longitude), so combine them with np.logical_and():

condition = np.logical_and(data.lat > 10.0, data.lon < 50.0)
box = data.where(condition)

Then use DataArray.argmax() across all the dimensions of the result to find the indices of the maximum values.

inds_of_max = box.argmax(dims=['lat', 'lon'])

Pass those indices to your latitude/longitude coordinate arrays to get the (lat, lon) pair you want.

lat, lon = data.lat[inds_of_max], data.lon[inds_of_max]

(This would probably be better placed on stackoverflow than here but doesn't matter)

[shoyer]

In fact, this was already asked on StackOverflow :)
https://stackoverflow.com/questions/40179593/how-to-get-the-coordinates-of-the-maximum-in-xarray

I'm going to close this, but feel free to comment or reopen if you have any further questions.