VectorField class

class PyFields.core.vectorfield.VectorField(axis_x, axis_y, comp_x, comp_y, mask=None, unit_x='', unit_y='', unit_values='')

Bases: PyFields.core.field.Field

Class representing a vector field (2D field, with two components on each point).

change_unit(axis, new_unit)

Change the unit of an axis.

Parameters:

• axis (string) – ‘y’ for changing the profile y axis unit ‘x’ for changing the profile x axis unit ‘values’ or changing values unit
• new_unit (Unum.unit object or string) – The new unit.

comp_x

comp_x_as_sf

comp_y

comp_y_as_sf

copy()

Return a copy of the vectorfield.

crop(intervx=None, intervy=None, ind=False, inplace=False)

Crop the vector field.

Parameters:

• intervx (array, optional) – Wanted interval along x.
• intervy (array, optional) – Wanted interval along y.
• ind (boolean, optional) – If ‘True’, intervals are understood as indices along axis. If ‘False’ (default), intervals are understood in axis units.
• inplace (boolean, optional) – If ‘True’, the field is croped in place, else (default), a copy is returned.

crop_masked_border(hard=False, inplace=False)

Crop the masked border of the field in place or not.

Parameters:hard (boolean, optional) – If ‘True’, partially masked border are croped as well.

display(component=None, kind=None, annotate=True, **plotargs)

Display the vector field.

Parameters:

• component (string, optional) – Component to display, can be ‘V’, ‘x’, ‘y’, ‘magnitude’ or ‘mask’
• kind (string, optinnal) – can be ‘quiver’, ‘stream’, ‘imshow’, ‘contour’, ‘contourf’
• annotate (boolean) – If True (default) add label and legedn to the graph.
• **plotargs (dict) – Arguments passed to the plotting function.

Returns:

fig – Reference to the displayed figure.

Return type:

figure reference

dtype

extend(nmb_left=0, nmb_right=0, nmb_up=0, nmb_down=0, value=None, inplace=False, ind=True)

Add columns and/or lines of masked values to the field.

Parameters:

• nmb_right, nmb_up, nmb_down (nmb_left,) – Number of lines/columns to add in each direction.
• inplace (bool) – If ‘True’, extend the field in place, else (default), return an extended copy of the field.

Returns:

Extended_field – Extended field.

Return type:

Field object

Note

If the axis values are not equally spaced, a linear extrapolation is used to obtain the new axis values.

fill(kind='linear', value=0.0, inplace=False, reduce_tri=True, crop=False)

Fill the masked parts of the vector field.

Parameters:

• kind (string, optional) – Type of algorithm used to fill. ‘value’ : fill with the given value ‘nearest’ : fill with the nearest value ‘linear’ (default): fill using linear interpolation (Delaunay triangulation) ‘cubic’ : fill using cubic interpolation (Delaunay triangulation)
• value (number) – Value used to fill (for kind=’value’).
• inplace (boolean, optional) – If ‘True’, fill the vector field in place. If ‘False’ (default), return a filled version of the field.
• reduce_tri (boolean, optional) – If ‘True’, treatment is used to reduce the triangulation effort (faster when a lot of masked values) If ‘False’, no treatment (faster when few masked values)
• crop (boolean, optional) – If ‘True’, SF borders are croped before filling.

get_histograms(bins=200, cum=False, normalized=False)

Return a vectorfield component histograms.

Parameters:

• cum (boolean) – If True, get a cumulative histogram.
• normalized (boolean) – If True, normalize the histogram.
• bins (integer) – Number of bins (default to 200).

Returns:

histx, histy – Histograms.

Return type:

Profile objects.

get_interpolators(interp='linear')

Return the field interpolators.

Parameters:kind ({‘linear’, ‘cubic’, ‘quintic’}, optional) – The kind of spline interpolation to use. Default is ‘linear’. Returns:Interpolators for each components Return type:interpx, interpy

Example

>>> interp = SF.get_interpolator(interp='linear')
>>> print(interp(4, 5.3))
... [34.3]
>>> print(interp([3, 4, 5], 5.3))
... [23, 34.3, 54]

get_norm(norm=2)

Return the field norm.

Parameters:norm (positive integer) – Norm order. Returns:norm – Norm. Return type:number

get_profile(x=None, y=None, component='x', ind=False, interp='linear')

Return a profile of the vector field, at the given position. If position is an interval, the fonction return an average profile in this interval.

Parameters:

• y (x,) – Position of the wanted profile.
• component (string in ['x', 'y']) – Component to get a profile from. (default to ‘x’)
• ind (boolean) – If ‘True’, position has to be given in indices If ‘False’ (default), position has to be given in axis unit.
• interp (string in ['nearest', 'linear']) – if ‘nearest’, get the profile at the nearest position on the grid, if ‘linear’, use linear interpolation to get the profile at the exact position

Returns:

profile – Wanted profile

Return type:

prof.Profile object

get_props()

Print the VectorField main properties

get_value(x, y, ind=False, unit=False)

Return the vector field components on the point (x, y).

Parameters:

• y (x,) – Positions where to get the components.
• ind (boolean) – If ‘True’, x and y are indices, else (default), x and y are in axis units
• unit (boolean) – If ‘True’, also return the components unities. (default to False)

magnitude

Return a scalar field with the velocity field magnitude.

magnitude_as_sf

Return a scalarfield with the velocity field magnitude.

make_evenly_spaced(interp='linear', res=1, inplace=False)

Use interpolation to make the field evenly spaced.

Parameters:

• interp ({‘linear’, ‘cubic’, ‘quintic’}, optional) – The kind of spline interpolation to use. Default is ‘linear’.
• res (number) – Resolution of the resulting field. A value of 1 meaning a spatial resolution equal to the smallest space along the two axis for the initial field. A value of 2 means half this resolution.
• inplace (boolean) – If True, modify the vector field in place, else, return a modified version of it.

mask

mask_as_sf

max

mean

min

reduce_resolution(fact, inplace=False)

Reduce the spatial resolution of the vector field by a factor ‘fact’.

Parameters:

• fact (int) – Reducing factor.
• inplace (boolean, optional) –

  .

rotate(angle, inplace=False)

Rotate the vector field.

Parameters:

• angle (integer) – Angle in degrees (signe in trigonometric convention). In order to preserve the orthogonal grid, only multiples of 90° are accepted.
• inplace (boolean, optional) – If True, the field is rotated in place, else (default), a rotated copy is returned.

Returns:

rotated_field – Rotated field.

Return type:

Field object

scale(scalex=None, scaley=None, scalev=None, inplace=False)

Scale the VectorField.

Parameters:

• scaley, scalev (scalex,) – Scale for the axis and the values.
• inplace (boolean) –

  .

smooth(tos='uniform', size=None, inplace=False, **kw)

Smooth the vectorfield.

Warning : fill up the field (should be used carefully with masked field borders)

Parameters:

• tos (string, optional) – Type of smoothing, can be ‘uniform’ (default) or ‘gaussian’ (See ndimage module documentation for more details)
• size (number, optional) – Size of the smoothing (is radius for ‘uniform’ and sigma for ‘gaussian’) in indice number. Default is 3 for ‘uniform’ and 1 for ‘gaussian’.
• inplace (boolean, optional) – If True, Field is smoothed in place, else, the smoothed field is returned.
• kw (dic) – Additional parameters for ndimage methods (See ndimage documentation)

std

theta

Return a scalar field with the vector angle (in reference of the unit_y vector [1, 0]).

Parameters:low_velocity_filter (number) – If not zero, points where V < Vmax*low_velocity_filter are masked. Returns:theta_sf – Contening theta field. Return type:sf.ScalarField object

theta_as_sf

Return a scalarfield with the velocity field angles.

unit_values