get_ratio_image¶

sherpa.astro.ui.get_ratio_image(id=None)¶

Return the data used by image_ratio.

Parameters:	id (int or str, optional) – The data set. If not given then the default identifier is used, as returned by get_default_id.
Returns:	ratio_img – The `y` attribute contains the ratio values as a 2D NumPy array.
Return type:	a sherpa.image.RatioImage instance
Raises:	`sherpa.utils.err.DataErr` – If the data set is not 2D. `sherpa.utils.err.IdentifierErr` – If the data set does not exist or a source expression has not been set.

See also

get_resid_image(): Return the data used by image_resid.
contour_ratio(): Contour the ratio of data to model.
image_ratio(): Display the ratio (data/model) for a data set in the image viewer.

Examples

Return the ratio data for the default data set:

>>> rinfo = get_ratio_image()