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'''
Helper to process mesh based data
=================================
Data that is distributed over a geometrical body, e.g. a stress tensor
distribution on a component, is usually transported via a mesh. The
meshes are a list of items (e.g. nodes or elements of a FEM mesh),
each being described by the geometrical coordinates and the local data
values, like for example the local stress tensor data.
In a plain mesh (see :class:`PlainMeshAccessor`) there is no further
relation between the items is known, whereas a complete FEM mesh (see
:class:`MeshAccessor`) there is also information on the connectivity
of the nodes and elements.
Examples
--------
Read in a mesh from a vmap file:
>>> df = (vm = pylife.vmap.VMAPImport('demos/plate_with_hole.vmap')
.make_mesh('1', 'STATE-2')
.join_variable('STRESS_CAUCHY')
.join_variable('DISPLACEMENT')
.to_frame())
>>> df.head()
x y z S11 S22 S33 S12 S13 S23 dx dy dz
element_id node_id
1 1734 14.897208 5.269875 0.0 27.080811 6.927080 0.0 -13.687358 0.0 0.0 0.005345 0.000015 0.0
1582 14.555333 5.355806 0.0 28.319006 1.178649 0.0 -10.732705 0.0 0.0 0.005285 0.000003 0.0
1596 14.630658 4.908741 0.0 47.701195 5.512213 0.0 -17.866833 0.0 0.0 0.005376 0.000019 0.0
4923 14.726271 5.312840 0.0 27.699907 4.052865 0.0 -12.210032 0.0 0.0 0.005315 0.000009 0.0
4924 14.592996 5.132274 0.0 38.010101 3.345431 0.0 -14.299768 0.0 0.0 0.005326 0.000013 0.0
Get the coordinates of the mesh.
>>> df.plain_mesh.coordinates.head()
x y z
element_id node_id
1 1734 14.897208 5.269875 0.0
1582 14.555333 5.355806 0.0
1596 14.630658 4.908741 0.0
4923 14.726271 5.312840 0.0
4924 14.592996 5.132274 0.0
Now the same with a 2D mesh:
>>> df.drop(columns=['z']).plain_mesh.coordinates.head()
x y
element_id node_id
1 1734 14.897208 5.269875
1582 14.555333 5.355806
1596 14.630658 4.908741
4923 14.726271 5.312840
4924 14.592996 5.132274
'''
__author__ = "Johannes Mueller"
__maintainer__ = __author__
import pandas as pd
from pylife import signal
[docs]@pd.api.extensions.register_dataframe_accessor("plain_mesh")
class PlainMeshAccessor(signal.PylifeSignal):
'''DataFrame accessor to access plain 2D and 3D mesh data, i.e. without connectivity
Raises
------
AttributeError
if at least one of the columns `x`, `y` is missing
Notes
-----
The PlainMeshAccessor describes meshes whose only geometrical
information is the coordinates of the nodes or elements. Unlike
:class:`MeshAccessor` they don't know about connectivity, not even
about elements and nodes.
See also
--------
:class:`MeshAccessor`: accesses meshes with connectivity information
:func:`pandas.api.extensions.register_dataframe_accessor()`: concept of DataFrame accessors
'''
def _validate(self, obj, validator):
self._coord_keys = ['x', 'y']
validator.fail_if_key_missing(obj, self._coord_keys)
if 'z' in obj.columns:
self._coord_keys.append('z')
@property
def coordinates(self):
'''Returns the coordinate colums of the accessed DataFrame
Returns
-------
coordinates : pandas.DataFrame
The coordinates `x`, `y` and if 3D `z` of the accessed mesh
'''
return self._obj[self._coord_keys]
[docs]@pd.api.extensions.register_dataframe_accessor("mesh")
class MeshAccessor(PlainMeshAccessor):
'''DataFrame accessor to access FEM mesh data (2D and 3D)
Raises
------
AttributeError
if at least one of the columns `x`, `y` is missing
AttributeError
if the index of the DataFrame is not a two level MultiIndex
with the names `node_id` and `element_id`
Notes
-----
The MeshAccessor describes how we expect FEM data to look like. It
consists of nodes identified by `node_id` and elements identified
by `element_id`. A node playing a role in several elements and an
element consists of several nodes. So in the DataFrame a `node_id`
can appear multiple times (for each element, the node is playing a
role in). Likewise each `element_id` appears multiple times (for
each node the element consists of).
The combination `node_id`:`element_id` however, is unique. So the
table is indexed by a :class:`pandas.MultiIndex` with the level
names `node_id`, `element_id`.
See also
--------
:class:`PlainMeshAccessor`: accesses meshes without connectivity information
:func:`pandas.api.extensions.register_dataframe_accessor()`: concept of DataFrame accessors
Examples
--------
For an example see :mod:`meshplot`.
'''
def _validate(self, obj, validator):
super(MeshAccessor, self)._validate(obj, validator)
if set(obj.index.names) != set(['element_id', 'node_id']):
raise AttributeError("A mesh needs a pd.MultiIndex with the names `element_id` and `node_id`")