Other Graphics Database Facilities

Various other facilities related to the graphics database exist as well as those described in the previous section. This section gives a brief description of a few more:

• A `label' can be associated with a picture, using application PICLABEL. This provides a convenient `handle' by which pictures can be referred to. For instance:

       % piclabel fred
  

  will give the label FRED to the current picture. This picture could be made current again at a later time by re-selecting it using PICSEL:

       % picsel fred
  

  Any label associated with a picture is displayed in the list produced by PICLIST.

• PICDEF has one further mode--Array. This enables you to create an $n\times m$ grid of new FRAME pictures. It also has a mechanism for labelling all the pictures, so you can easily switch between the elements of the picture array. You might use the following command in a shell script to display a series of up to twelve spectra:

       % picdef mode=a prefix=spec xpic=3 ypic=4
  

  The bottom-left picture would be labelled SPEC1 and the rest are numbered in sequence from left to right to SPEC12--the top-right picture. You'd call PICSEL to select each picture in turn via a while loop in a C-shell script. Since this is a common operation a shorthand command, PICGRID, is available. For instance:

       % picgrid 3 4
  

  is equivalent to the previous example, except that the pictures are labelled 1 to 12.

• You can see that montages of pictures can rapidly be built. Occasionally, you will want some earlier picture to become the current picture. As we've seen, a labelled picture can be recalled via PICSEL, but not all pictures will be labelled, especially ones with name DATA, because of the rule that applications must not change the current picture. Another way to select a new current picture is via the command PICCUR. It displays a cursor. Move the cursor to lie on top of the picture you require and select a point following the instructions (usually by pressing the left-button of the mouse), then exit (normally by hitting the right-hand mouse button). Generally, this will be fine, but you can have cases where one plot is still visible through a transparent plot drawn subsequently. If the later picture extends entirely over the image you require, PICCUR will not let you access it. The moral is ``be careful when arranging your pictures''. A picture may only be partially obscured, so by moving the cursor around and hitting the left-hand button you can often find a portion that is topmost. PICCUR reports the name, comment and the label (if it there is one) of the picture in which the cursor is located to assist you. It is usually quite obvious where pictures begin and end, so in practice it is easier than described here.

• If you do get lost or forget what and where the current picture is, the GDSTATE command will come to your rescue. You can even plot an outline with the OUTLINE keyword if you can't visualise the device co-ordinates. In the following example, the current picture does not have a label. If it did this too would be listed by GDSTATE:

       % gdstate
  
       Status of the xwindows window graphics device...
  
          The current picture is a FRAME picture.
          Comment: KAPPA_PICDEF
          Current co-ordinate Frame: BASEPIC
  
       Picture bounds in the BASEPIC Frame:
          Axis 1 (X) : 0.516 to 0.891
          Axis 2 (Y) : 0.010 to 0.605