get_data_plot

Context: data

Synopsis

Return a plot, contour, or image of the data, or the associated preferences

Syntax

get_data_plot( [id] )
get_data_plot_prefs()
get_data_contour( [id] )
get_data_contour_prefs()
get_data_image( [id] )

Description

id - the id of the dataset to use; if not given, uses the default dataset id (id=1 by default, see "ahelp get_default_id")

get_data_plot

The get_data_plot command returns a data plot object which holds references to various plot preferences and data arrays. The attributes are:

Field name	Description
x	The bin centers (independent variable)
y	The value of the dependent variable
yerr	The error on y
xerr	The half-width of the bin
xlabel	The label for the X axis
ylabel	The label for the Y axis
title	The plot title
plot_prefs	The preferences for the plot

Note that the show_data command ("ahelp show_data") is recommended to simply print the current data to the screen.

get_data_plot_prefs

The get_data_plot_prefs command returns a dictionary of data plot preferences. For example:

{'errstyle': 'line',
 'linestyle': 0,
 'symbolfill': False,
 'symbolsize': 3,
 'symbolstyle': 4,
 'yerrorbars': True}

Users can change preferences as desired in the set returned by this function, as shown below in the examples. These preferences changes the appearance of data plotted using the following commands: plot_data(), plot_bkg(), plot_ratio(), and the "fit" versions of these commands, such as plot_fit(), plot_bkg_fit(), and plot_fit_delchi().

get_data_contour

The get_data_contour command returns a data contour object which holds references to various plot preferences and data arrays. The attributes are:

Field name	Description
x0	The coordinate values for the first axis as a 1D array
x1	The coordinate values for the second axis as a 1D array
y	The data value at each point of (x0,x1) as a 1D array
levels	The levels used for drawing contours
xlabel	The label for the X axis
ylabel	The label for the Y axis
title	The plot title
contour_prefs	The preferences for the plot

get_data_contour_prefs

The get_data_contour_prefs command returns a dictionary of data contour preferences. By default, the set is empty:

{}

get_data_image

The get_data_image command returns an image object which holds the reference to the image array. The attributes are:

Field name	Description
name	A label for the object
y	The image data (as a 2D array)
eqpos	Information on the world coordinate system (if available)
sky	Information on the physical coordinate system (if available)

Example 1

sherpa> p = get_data_plot_prefs()
sherpa> p["xlog"] = True
sherpa> p["ylog"] = True
sherpa> p["symbolfill"] = True
sherpa> p["symbolstyle"] = chips_diamond
sherpa> p["symbolcolor"] = "blue"
sherpa> p["errcolor"] = "yellow"
sherpa> p["errstyle"] = "capped"
sherpa> p["linetyle"] = chips_solid
sherpa> p["linecolor"] = "orange"
sherpa> p["linethickness"] = 2

Change the defaults for plot_data() so that:

both the X and Y axes will be drawn using a log scale;
symbols will be drawn as blue, filled diamonds;
errors will be drawn as yellow bars with caps on the end;
the points will be connected using a solid, orange line of thickness 2.

Example 2

sherpa> d = get_data_plot()
sherpa> erase()
sherpa> add_curve(d.x, d.y, d.yerr)
sherpa> set_plot_xlabel(d.xlabel)
sherpa> set_plot_ylabel(d.ylabel)
sherpa> set_plot_title(d.title)

Manually create a plot of the data, similar to that created by the plot_data() command.

Example 3

sherpa> get_data_contour("src")

Return a data contour object for dataset "src".

Bugs

See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.