# WCSAxes¶

class astropy.visualization.wcsaxes.WCSAxes(fig, rect, wcs=None, transform=None, coord_meta=None, transData=None, slices=None, frame_class=<class 'astropy.visualization.wcsaxes.frame.RectangularFrame'>, **kwargs)[source] [edit on github]

The main axes class that can be used to show world coordinates from a WCS.

Parameters: fig : Figure The figure to add the axes to rect : list The position of the axes in the figure in relative units. Should be given as [left, bottom, width, height]. wcs : WCS, optional The WCS for the data. If this is specified, transform cannot be specified. transform : Transform, optional The transform for the data. If this is specified, wcs cannot be specified. coord_meta : dict, optional A dictionary providing additional metadata when transform is specified. This should include the keys type, wrap, and unit. Each of these should be a list with as many items as the dimension of the WCS. The type entries should be one of longitude, latitude, or scalar, the wrap entries should give, for the longitude, the angle at which the coordinate wraps (and None otherwise), and the unit should give the unit of the coordinates as Unit instances. transData : Transform, optional Can be used to override the default data -> pixel mapping. slices : tuple, optional For WCS transformations with more than two dimensions, we need to choose which dimensions are being shown in the 2D image. The slice should contain one x entry, one y entry, and the rest of the values should be integers indicating the slice through the data. The order of the items in the slice should be the same as the order of the dimensions in the WCS, and the opposite of the order of the dimensions in Numpy. For example, (50, 'x', 'y') means that the first WCS dimension (last Numpy dimension) will be sliced at an index of 50, the second WCS and Numpy dimension will be shown on the x axis, and the final WCS dimension (first Numpy dimension) will be shown on the y-axis (and therefore the data will be plotted using data[:, :, 50].transpose()) frame_class : type, optional The class for the frame, which should be a subclass of BaseFrame. The default is to use a RectangularFrame

Methods Summary

 draw(renderer[, inframe]) Draw everything (plot lines, axes, labels) draw_wcsaxes(renderer) get_coords_overlay(frame[, coord_meta]) get_tightbbox(renderer) Return the tight bounding box of the axes. get_transform(frame) Return a transform from the specified frame to display coordinates. get_xlabel() Get the xlabel text string. get_ylabel() Get the ylabel text string. grid([b, axis, which]) Plot gridlines for both coordinates. imshow(X, *args, **kwargs) Wrapper to Matplotlib’s imshow(). plot_coord(*args, **kwargs) Plot SkyCoord or BaseCoordinateFrame objects onto the axes. reset_wcs([wcs, slices, transform, coord_meta]) Reset the current Axes, to use a new WCS object. set_xlabel(label[, labelpad]) Set the label for the x-axis. set_ylabel(label[, labelpad]) Set the label for the y-axis.

Methods Documentation

draw(renderer, inframe=False)[source] [edit on github]

Draw everything (plot lines, axes, labels)

draw_wcsaxes(renderer)[source] [edit on github]
get_coords_overlay(frame, coord_meta=None)[source] [edit on github]
get_tightbbox(renderer)[source] [edit on github]

Return the tight bounding box of the axes. The dimension of the Bbox in canvas coordinate.

If call_axes_locator is False, it does not call the _axes_locator attribute, which is necessary to get the correct bounding box. call_axes_locator==False can be used if the caller is only intereted in the relative size of the tightbbox compared to the axes bbox.

get_transform(frame)[source] [edit on github]

Return a transform from the specified frame to display coordinates.

This does not include the transData transformation

Parameters: frame : WCS or Transform or str The frame parameter can have several possible types: WCS instance: assumed to be a transformation from pixel to world coordinates, where the world coordinates are the same as those in the WCS transformation used for this WCSAxes instance. This is used for example to show contours, since this involves plotting an array in pixel coordinates that are not the final data coordinate and have to be transformed to the common world coordinate system first. Transform instance: it is assumed to be a transform to the world coordinates that are part of the WCS used to instantiate this WCSAxes instance. 'pixel' or 'world': return a transformation that allows users to plot in pixel/data coordinates (essentially an identity transform) and world (the default world-to-pixel transformation used to instantiate the WCSAxes instance). 'fk5' or 'galactic': return a transformation from the specified frame to the pixel/data coordinates. BaseCoordinateFrame instance.
get_xlabel()[source] [edit on github]

Get the xlabel text string.

get_ylabel()[source] [edit on github]

Get the ylabel text string.

grid(b=None, axis='both', *, which='major', **kwargs)[source] [edit on github]

Plot gridlines for both coordinates.

Standard matplotlib appearance options (color, alpha, etc.) can be passed as keyword arguments. This behaves like matplotlib.axes.Axes except that if no arguments are specified, the grid is shown rather than toggled.

Parameters: b : bool Whether to show the gridlines.
imshow(X, *args, **kwargs)[source] [edit on github]

Wrapper to Matplotlib’s imshow().

If an RGB image is passed as a PIL object, it will be flipped vertically and origin will be set to lower, since WCS transformations - like FITS files - assume that the origin is the lower left pixel of the image (whereas RGB images have the origin in the top left).

All arguments are passed to imshow().

plot_coord(*args, **kwargs)[source] [edit on github]

Plot SkyCoord or BaseCoordinateFrame objects onto the axes.

The first argument to plot_coord() should be a coordinate, which will then be converted to the first two parameters to matplotlib.axes.Axes.plot. All other arguments are the same as matplotlib.axes.Axes.plot. If not specified a transform keyword argument will be created based on the coordinate.

Parameters: coordinate : SkyCoord or BaseCoordinateFrame The coordinate object to plot on the axes. This is converted to the first two arguments to matplotlib.axes.Axes.plot.

See also

matplotlib.axes.Axes.plot
This method is called from this function with all arguments passed to it.
reset_wcs(wcs=None, slices=None, transform=None, coord_meta=None)[source] [edit on github]

Reset the current Axes, to use a new WCS object.

set_xlabel(label, labelpad=1, **kwargs)[source] [edit on github]

Set the label for the x-axis.

Parameters: Other Parameters: xlabel : str The label text. labelpad : scalar, optional, default: None Spacing in points between the label and the x-axis. **kwargs : Text properties Text properties control the appearance of the label.

See also

text
for information on how override and the optional args work
set_ylabel(label, labelpad=1, **kwargs)[source] [edit on github]

Set the label for the y-axis.

Parameters: Other Parameters: ylabel : str The label text. labelpad : scalar, optional, default: None Spacing in points between the label and the y-axis. **kwargs : Text properties Text properties control the appearance of the label.

See also

text
for information on how override and the optional args work