aggregate: aggregate field values

aggregate(grid, field, method, **kwds)[source]

Calculate an aggreggate value on a Landlab grid field.

aggregate calculates aggregate values on the core nodes of the model grid. It supports all methods in the numpy namespace that reduce an array to a scalar.

Parameters

  • grid (Landlab model grid) –

  • field (str) – An at-node Landlab grid field that is present on the model grid.

  • method (str) – The name of a numpy namespace method.

  • **kwds – Any additional keyword arguments needed by the method.

Returns

out – The aggregate value.

Return type

float

Examples

First an example that only uses the aggregate function.

>>> from landlab import RasterModelGrid
>>> from umami.calculations import aggregate
>>> grid = RasterModelGrid((10, 10))
>>> z = grid.add_zeros("node", "topographic__elevation")
>>> z += grid.x_of_node + grid.y_of_node

aggregate supports all functions in the numpy namespace. Here we show mean and percentile. The latter of which takes an additional argument, q.

>>> aggregate(grid, "topographic__elevation", "mean")
9.0
>>> aggregate(grid, "topographic__elevation", "percentile", q=10)
5.0

Next, the same calculations are shown as part of an umami Metric.

>>> from io import StringIO
>>> from umami import Metric
>>> file_like=StringIO('''
... me:
...     _func: aggregate
...     method: mean
...     field: topographic__elevation
... ep10:
...     _func: aggregate
...     method: percentile
...     field: topographic__elevation
...     q: 10
... ''')
>>> metric = Metric(grid)
>>> metric.add_from_file(file_like)
>>> metric.names
['me', 'ep10']
>>> metric.calculate()
>>> metric.values
[9.0, 5.0]