Accessing individual elements in xarray DataArray

Question

I'm using xarray.DataArray for loading data. One of the variables 'mtime' in the data looks like:

xarray.DataArray 'mtime' (mtimedim: 3) 
array([149,  13,   0]) 

Coordinates:     time     datetime64[ns] 2009-05-29T13:00:00     
    lon      float64 -150.0     
    lat      float64 11.25     
    LBC      float64 ... 
Dimensions without coordinates: mtimedim 
Attributes:     long_name:  model times (day, hour, minute)     
units:      day, hour, minute

I wish to fetch the first element 149 in the DataArray. I would like to fetch it as an individual element and not as xarray. I'm currently doing it as

data.mtime.to_series()[0]

And my output is 149. Is this the right way to do it or is there a better approach? Appreciate your help. Thanks.

Keisuke FUJII · Accepted Answer · 2018-07-11 08:20:50Z

2

You can do either

data[0].values  # -> gives 0d-np.array
data[0].values.item()  # -> gives a scalar
data.values[0]  # -> gives a scalar

.values returns a raw np.array. .data returns a np.array or dask.array depending on the backend.

answered Jul 11, 2018 at 8:20

Keisuke FUJII

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5 Comments

SGI Over a year ago

Thanks for your reply. When data contains only one element, I get the error - IndexError: too many indices for array when I try data.values[0] and data[0].values. I don't quite understand the error message. For me, it looks like there is more data and I'm not using the right number of indices to access the data. Can you please clarify why I get this message and what it means?

Keisuke FUJII Over a year ago

I think your data is 0d-array. What will happen if you do data.values.item()?

SGI Over a year ago

You are right. Data is 0d-array.

<xarray.DataArray 'Z' ()> array(50476781.92) Coordinates:     time     datetime64[ns] 2009-05-29T02:00:00     LBC      float64 -7.0     lat      int32 10     ilev     float64 6.89     lon      int32 78 Attributes:     long_name:  GEOPOTENTIAL HEIGHT     units:      cm  data[0].values #--> IndexError: too many indices data[0].values.item() #--> IndexError: too many indices data.values[0] #--> IndexError: too many indices for array data.values #--> array(50476781.92) (array) data.values.item() #--> 50476781.92 (scalar)

SGI Over a year ago

Sorry for the bad formatting. I'm new to stackoverflow and trying to understand how to make the code look good. I still don't understand the error message 'Too many indices' or is it actually 'too less indices'?

Michael Delgado Over a year ago

noting that xarray now includes da.item() for 0-D DataArrays, so the example here for retrieving a scalar could simply be data[0].item()

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