# MaterialLayers: Add material layers to a landlab grid¶

class MaterialLayers(number_of_stacks, allocated=0)[source]

Track MaterialLayers where each layer has some material in it.

MaterialLayers are meant to represent a layered object in which each layer has some material in it. If erosion occurs, no new layer is created. These layers stand in contrast to the EventLayers for which each event is represented by a layer.

MaterialLayers is likely a more memory efficent data structure than EventLayers as it does not record erosion as an array of zeros.

Parameters: number_of_stacks (int) – Number of layer stacks to track.
allocated
dz
thickness
number_of_layers
number_of_stacks
surface_index
z
add()[source]
get_surface_values()

Examples

>>> from landlab.layers.materiallayers import MaterialLayers


Create an empty layer stack with 5 stacks.

>>> layers = MaterialLayers(5)
>>> layers.number_of_stacks
5
>>> layers.number_of_layers
0


Add a layer with a uniform thickness.

>>> layers.add(1.5)
>>> layers.number_of_layers
1
>>> layers.dz
array([[ 1.5,  1.5,  1.5,  1.5,  1.5]])


MaterialLayers will combine layers if they have the same attributes. Adding a second layer with uneven thickness. Will increment the first layers thickness. This stands in contrast with EventLayers which will track each addition as a separate entry in the layers datastructure.

>>> layers.add([1., 2., 3., 5., 0.])
>>> layers.dz
array([[ 2.5,  3.5,  4.5,  6.5,  1.5]])


Adding a layer with negative thickness will remove material from the layers. Unlike EventLayers, it will not add a layer of zeros that represent an event with no deposition.

>>> layers.add(-1)
>>> layers.dz
array([[ 1.5,  2.5,  3.5,  5.5,  0.5]])


Get the index value of the layer within each stack at the topographic surface.

>>> layers.surface_index
array([0, 0, 0, 0, 0])


See the example in the add method to learn how MaterialLayers behaves if material properties are also tracked.

add(dz, **kwds)[source]

Add a layer to the MaterialLayers stacks.

Parameters: dz (float or array_like) – Thickness to add to each stack.

Examples

>>> from landlab.layers.materiallayers import MaterialLayers


Create an empty layer stack with 3 stacks.

>>> layers = MaterialLayers(3)
>>> layers.number_of_layers
0


To add a layer of uniform thickness to every stack.

>>> layers.add(1.5)
>>> layers.number_of_layers
1
>>> layers.dz
array([[ 1.5,  1.5,  1.5]])


Add a second layer with uneven thickness.

>>> layers.add([1., 2., .5])
>>> layers.dz
array([[ 2.5,  3.5,  2. ]])


Because the attributes of this layer and the previous layer are the same (e.g. they don’t exist), MaterialLayer will combined them. This is the primary difference between MaterialLayers and EventLayers.

Adding a layer with negative thickness will remove material from the top of the stack.

>>> layers.add(-1)
>>> layers.dz
array([[ 1.5,  2.5,  1. ]])
>>> layers.number_of_layers
1


Use keywords to track properties of each layer. For instance, here we create a new stack and add a layer with a particular type and a particular size. You can access the layer properties as if the object were a dictionary.

>>> layers = MaterialLayers(3)
>>> layers.dz
array([[ 1.,  1.,  1.]])
>>> layers['type']
array([[ 3.,  3.,  3.]])


As you can see, there is no rule that says you can’t use a string as the value of an attribute.

Adding a layer with the same attributes as the entire surface of the MaterialLayers will result in the layers being combined.

>>> layers.add(1., type=3., size='sand')
>>> layers.add([2, -1, 0], type=3., size='sand')
>>> layers.dz
array([[ 4.,  1.,  2.]])


Adding material with different attributes results in the creation of a new layer.

>>> layers.add(2., type=6., size='sand')
>>> layers.dz
array([[ 4.,  1.,  2.],
[ 2.,  2.,  2.]])
>>> layers['type']
array([[ 3.,  3.,  3.],
[ 6.,  6.,  6.]])
>>> np.all(layers['size'] == [['sand', 'sand', 'sand'],
...                           ['sand', 'sand', 'sand']])
True


Attributes for each layer will exist even if part the the layer is associated with erosion.

>>> layers.add([-2, -1, 1], type=8., size='gravel')
>>> layers.dz
array([[ 4.,  1.,  2.],
[ 0.,  1.,  2.],
[ 0.,  0.,  1.]])
>>> layers['type']
array([[ 3.,  3.,  3.],
[ 6.,  6.,  6.],
[ 8.,  8.,  8.]])


To get the values at the surface of the layer stack:

>>> layers.get_surface_values('type')
array([ 3.,  6.,  8.])


Removing enough material such that an entire layer’s thickness is no longer present, results in that layer no longer being tracked. This is another difference between MaterialLayers and EventLayers.

>>> layers.add([ 0., 0., -1. ])
>>> layers.dz
array([[ 4.,  1.,  2.],
[ 0.,  1.,  2.]])
>>> layers['type']
array([[ 3.,  3.,  3.],
[ 6.,  6.,  6.]])
>>> np.all(layers['size'] == [['sand', 'sand', 'sand'],
...                           ['sand', 'sand', 'sand']])
True
>>> layers.number_of_layers
2


If attributes (like age and size in this example) are tracked, a layer will be combined with the surface layer only if all attributes are the same across the entire layer. Right now, the surface values vary.

>>> layers.get_surface_values('type')
array([ 3.,  6.,  6.])
>>> np.all(layers.get_surface_values('size') == ['sand', 'sand', 'sand'])
True


Since the surface has different types, adding material will create a new layer.

>>> layers.add(3., type=6., size='sand')
>>> layers.dz
array([[ 4.,  1.,  2.],
[ 0.,  1.,  2.],
[ 3.,  3.,  3.]])
>>> layers['type']
array([[ 3.,  3.,  3.],
[ 6.,  6.,  6.],
[ 6.,  6.,  6.]])
>>> layers.number_of_layers
3


But now, the entire surface has the qualities of type = 6. and size = ‘sand’, so layers will be combined. This even works if the thickness of the new layer includes both erosion and deposition.

>>> layers.add([ -3.5, 0., 2. ], type=6., size='sand')
>>> layers.dz
array([[ 3.5,  1. ,  2. ],
[ 0. ,  1. ,  2. ],
[ 0. ,  3. ,  5. ]])
>>> layers['type']
array([[ 3.,  3.,  3.],
[ 6.,  6.,  6.],
[ 6.,  6.,  6.]])
>>> layers.number_of_layers
3

is_compatible(dz, **kwds)[source]

Check if a new layer is compatible with the existing top layer.

Parameters: dz (float or array_like) – Thickness to add to each stack. True if the new layer is compatible, otherwise False. bool
class MaterialLayersMixIn[source]

Bases: object

MixIn that adds a MaterialLayers attribute to a ModelGrid.

material_layers

MaterialLayers for each cell.