3.13 The region extraction window

This window is used to cut out or remove sections from the current spectrum. The sections are defined as a series of graphics ranges that you draw on the plot display area.


To add a region press the Add button and then drag out a region in the display area of the plot window. This should result in the creation of a green rectangular figure.

You can interact with the figure, moving it side-to-side and resizing it. To do this point at the figure and press the left mouse button. This ‘selects’ the figure and adds grips to its exterior. Note that it also becomes the selected row in the Coordinate ranges: table. To move the figure just drag it and to resize it drag a grip (the little black squares). The associated coordinate range in the table updates with these changes.

To add a second range just press Add and repeat. The ranges can be overlapped or not.

To fine tune the ranges you can edit the values in the ranges table, just point at the cell you want to change and double click the left mouse button. This should enable the text editing cursor. Just make the modifications you want and press <Return> to make the changes permanent. (Note: if your spectra have sky coordinates shown for the X axis, then you should use the same format for your edits).

To read a set of ranges from a disk file choose the File->Read ranges menu item. The format of the input file is simple. It should have two fields separated by whitespace or commas. Comments are indicated by lines starting with a hash (#) and are ignored.

When you’ve got the ranges that you want to extract, remove or replace by linear interpolation, press one of various the Cut, Remove or Interpolate buttons. This creates and displays a new spectrum on the global list called Cut <n> of <shortname>, that you can save to disk, or display in another plot etc. To just extract, remove or interpolate, one or a subset of the ranges select the rows in the ranges table and press the Cut Selected, Remove Selected or Interpolate Selected buttons.

To clear the ranges press the Reset button, but note that this also clears any spectra that have been created on the global list. To keep these just close the window.

When interpolating you will often just want to see the resultant spectrum, so there is a special Interpolate (Replace) action. That performs the interpolation, removes the current spectrum and then displays the result of interpolation. To go back from this change use the Reset (Replace) button (only undoes one change).

Accelerator keys