Working with Plots

In Mira AP, the term "plot" refers to displaying 1-dimensional data in the form of a 2-D graph. A special type of window exists to display and work with plots, known as a Plot Window. In working with images, plots are often created to show the relationship between image luminance and position, known as a Profile Plot (see example below), but a number of other types of plot are available within the software. Click here to view some examples of plot data.

Plot Types

Mira AP can create plots of the following types:

• The Column Profile command graphs image luminance along an image column.

• The Row Profilecommand graphs image luminance along an image row.

• The Radial Profile command graphs luminance versus distance in all directions around a point in an image.

• The Line Profile command graphs image luminance along an arbitrary drawn line.

• The Histogram command graphs the frequency of occurrence of different luminance values.

Comparing Line Profile and Row Profile Plots

The intensity profile of an image can be plotted using either the Column or Row Profile command or the Line Profile tool. There are some unique capabilities offered by each method.

Comparison of Profile Plot Types

Plot Coordinates

All of the profile plots show image luminance versus position or distance. For these types, Mira also provides the following coordinate system options:

Coordinate Axis:

• Use Pixel Coordinates to measure pixel position in column or row [number].

• Use World Coordinates to measure position in [arcseconds] relative to a coordinate in (RA, Dec).

• To change the default setting, see Plotting in World Coordinates.

• Luminance Axis:

  Luminance is displayed on the vertical axis of a profile plot and the horizontal axis of a histogram plot. The Luminance Axis label includes the units of luminance if the image header contains such information.

  Working with Plot Series

  A Plot Series is a collection of data points collected together. Usually these collections are related. For example, in a Column Profile plot, a plot series is a single sample of luminance versus position along a single line. A different series might be a sample of points parallel to the first, taken along a different column. Profile plots can show a single plot series or multiple plot series from samples along other lines. When multiple series are displayed in the same Plot Window, they may be visualized in the following ways:

• In Animate mode, the active plot series is displayed singly. The other series may be viewed by stepping or animating through the set using the Plot Animation Toolbar much the same way the Image Animation Toolbar steps through an Image Set.

• In Over-Plot mode, all plot series are displayed simultaneously as an "over-plot" on the same set of axes. If only 1 plot series is displayed, this is the default mode. In this mode, the Plot Animation Toolbar is hidden.

• To change the Plot Series Mode, see Changing the Plot Series Mode.

• Averaging Adjacent Lines

  Adjacent lines (columns or rows) may be combined to form a single line to be plotted. The name of the plot appears in the command menu from which the plot is created (see Plotting an Averaged Line).

  Plot Preferences and Attributes

• Preferences control how the plot is created from the image. This includes, for example, whether Pixel or World Coordinates are used and what colors are used for multiple plot series. These settings are changed in the Plot Preferences page of the Mira Preferences dialog.

• Attributes control the way the finished plot is displayed. You can change the axis scaling, colors, fonts, labels, tick marks, and other attributes using the pages of the Plot Attributes dialog.

Understanding Plot Captions

Caption Above the Plot Box

The Plot Caption is the text above the plot box and below the top window border. The Plot Caption tells you information about what was plotted. In particular, it may list the beginning and ending coordinates in (x,y) form for a Line Profile Plot or it may list the column and row range for a Column Profile or Row Profile plot. Below are some examples that show how to read the column,row range in the plot caption:

Example Regions Listed in the Plot Caption

You can change the plot caption using the Labels page of the Plot Attributes dialog.

Window Caption

The Plot Window caption lists the image name from which the plot was created and gives an abbreviation that describes the type of plot. The plot type is abbreviated and appended to the window caption in square brackets. For example, a Row Plot is signified by [RP] appended to the Plot window caption. These suffixes appear in the window list of the Window menu and in the Multi-tab Interface along the bottom border of Mira's main window.

Plot Name Suffixes

Related Topics

Plot Windows, Plotting Commands, Plot Coordinate System, Plotting an Averaged Line