# Create a generic time-mean functionΒΆ

This function applies to any kind of input array, as long as the “time” dimension is present.

```
>>> def time_mean(a, t1=None, t2=None):
... """ compute time mean between two instants
...
... Parameters:
... -----------
... a : DimArray
... must include a "time" dimension
... t1, t2 : same type as a.time (typically int or float)
... start and end times
...
... Returns:
... --------
... ma : DimArray
... time-average between t1 and t2
... """
... assert 'time' in a.dims, 'dimarray must have the "time" dimension'
... return a.swapaxes(0, 'time')[t1:t2].mean(axis='time')
```

```
>>> from dimarray import DimArray
>>> import numpy as np
```

```
>>> a = DimArray([1,2,3,4], axes=[[2000,2001,2002,2003]], dims=['time'])
>>> time_mean(a, 2001, 2003) # average over 2001, 2002, 2003
3.0
```

```
>>> a = DimArray([[1,2,3,4],[5,6,7,8]], axes=[['a','b'],[2000,2001,2002,2003]], dims=['items','time'])
>>> time_mean(a) # average over the full time axis
dimarray: 2 non-null elements (0 null)
0 / items (2): 'a' to 'b'
array([ 2.5, 6.5])
```