The Plot

Plotting data is done by using GreG. All GreG commands are available in CLASS.

Plotting spectra is controlled by several parameters

 
• SET UNIT Type defines the unit of the X axis, which may be C (for Channel number), V (for Velocity), F (for Frequency) or I (for Image).  
• LAS SET PLOT Type defines the plotting type PLOT (Normal or Histogram) ; Normal gives straight lines connecting the data points (this is the default since it is faster). Histogram gives a more realistic representation of spectroscopic data.  
• SET MODE X (or Y) Type defines the plotting limits in X or Y, where type stands for TOTAL (all channels plotted in X, complete scale in Y), AUTO (take the plotting limits in use when the spectrum was last written), or two numbers for fixed limits ; X or Y specify the axis on which the type is to apply. For X axis, the limits are in the current units (C, V or F). For F, specify the offset from the rest frequency in MHz (note: the caption and the numbers on the axis will refer to absolute rest frequencies).

Several commands result in plotting. These are :

 
• BOX, which plots the frame. The Y axes are labelled in temperature units ; the X axes may be in the following units : Velocity, Frequency, Image frequency, or Channel number. The upper X axis may be labelled in a different unit than that of the lower axis. Units for both axes are entered by the command   SET UNIT L U, where L and U stand for the units of lower and upper axes and may be any of V, F, I, or C. The second parameter U is optional ; if not entered, it defaults to L.

    BOX accepts the option /UNIT which specifies a unit temporarily different from the current one (given by the SET UNIT command). The parameter UPPER will modify only the unit for the upper axis of the frame. For instance : BOX /UNIT F UPPER will give velocities on the lower axis (if this is the current unit specified by SET UNIT V) and rest frequencies on the upper axis.

   

• SPECTRUM, which plots the spectrum, in the current mode, clipped into the current box. An offset may be given as argument to plot two spectra above each other for comparison.  
• TITLE, which writes a header above the frame. The title format is controlled by the SET FORMAT  command.  
• PLOT, which performs all of CLEAR; BOX; SPECTRUM; TITLE in a single operation.