SPLOT-Plots a spectrum

Description:

The SPLOT command will plot a spectrum on the current hard or soft graphics device.

Parameters:

SPECTRUM

The name of the spectrum to be plotted by SPLOT. It should be a 1-dimensional array.

HARDCOPY

If set, the plot is written to the device defined as the current hardcopy device. Generally, this is a disk file which will then have to printed. If HARDCOPY is not set, the plot will go to the current softcopy device. The hard and soft copy devices are specifed using the HARD and SOFT commands respectively.

WHOLE

If set, the whole of the spectrum is plotted. Otherwise, the limits plotted are determined by the values of XSTART and XEND, which you will be prompted for if they were not specified in the command string.

AUTOSCALE

If set, the plot is scaled so that all of the data to be plotted just fits on the display. Otherwise, the scale of the plot is determined by the values of HIGH and LOW, which you will be prompted for if they were not specified in the command string.

XSTART

The first X value to be plotted, in the units used by the data - angstroms, for example, if the data is wavelength calibrated. XSTART can be set before the start of the data, if necessary. RESET will set XSTART to the first X value in the data.

XEND

The last X value to be plotted, in the units used by the data - angstroms, for example, if the data is wavelength calibrated. XEND can be set after the end of the data, if necessary. RESET will set XEND to the last X value in the data.

HIGH

The maximum data value to be plotted - i.e. the top Y axis value for the plot.

LOW

The minimum data value to be plotted - i.e. the bottom Y axis value for the plot.

BIAS

A bias value applied to the data, usually to bias up a plot which is to be superimposed upon a previous plot of almost identical data values. This makes the comparison easier. BIAS N is essentially equivalent to setting HIGH and LOW down by an amount N, so can result in unexpected axis values if it is not accompanied by AXES=NO.

LABEL

The label that will appear at the top of the plot.

ERASE

Specifies that the screen is to be erased before the plot is made. Usually ERASE and AXES will not be set when a plot is superimposed on a previous one.

AXES

Specifies that the axes for the plot are to be drawn. These should be omitted if the plot is being superimposed on a previous one, or sometimes just to save plotting time.

LINES

Specifies that the plot is to made as a 'point-plot', in a 'join the dots' fashion. The alternative is a histogram plot. LINES will usually be a little faster, but messier, because the resolution of the plotting device will result in stepped lines.

COLOUR

The colour the data are to be plotted in. The axes are always plotted in white. The colours allowed are Blue, White, Red, Green, Black, Cyan, Magenta, Yellow. Using Black will have the effect of erasing anything where the data is plotted. This only works on the Grinnell.

THICKNESS

Only used for 'build' or 'hard' plots. It is used to increase the thickness of the lines plotted in order to increase legibility, particularly on the Versatec. Generally 1 or 3 is reasonable for the Versatec - depending on how well set up it is at the present, and 1 should be used for other devices.

See also:

FIGARO: ESPLOT, IPLOTS, MSPLOT.
KAPPA: LINPLOT, MLINPLOT.

Source comments:

 S P L O T    /    E S P L O T

 Produces a plot of a spectrum.  The plot is directed
 to the device defined by the user variables 'SOFT' and
 'HARD', and by the value of the command keyword 'HARDCOPY',
 so will appear immediately if these specify a video
 device (VT125, Args, etc.).  If a hardcopy device
 is specified, the file for that device will be produced,
 but SPLOT does not attempt to spool it off for printing.

 ESPLOT is similar to SPLOT, but plots error bars based on the
 errors in the data.

 Command parameters -

 SPECTRUM    The data to be plotted.  If this contains X-axis
             information, this will be used.  If not, the X-axis
             will just have to be the numbers from 1 to n.
 XSTART      The x-value at which plotting is to start.
 XEND        The x-value at which plotting is to end.
             (XSTART and XEND are not required if the
             WHOLE keyword is set.)
 HIGH        The maximum value to be used for the plot.
 LOW         The minimum value to be used for the plot.
 BIAS        A value used to displace the plot - BIAS is
             effectively a value added to the data before
             it is plotted. (It is implemented as a value
             subtracted from both HIGH and LOW.)
             (HIGH,LOW and BIAS are not required if the
             AUTOSCALE keyword is set.)
 LABEL       A label for the plot.
 COLOUR      The colour for the plot, assuming the display device
             supports it.  The axes are always white.
 THICKNESS   The width of the lines used for the plot.  This is
             only used for 'hard' & 'build' plots, and should
             really be 1 for anything other than a high-resolution
             device like a Versatec or a laser printer.

 Command keywords -

 AUTOSCALE   The program is to work out the values for HIGH
             and LOW, using the maximum and minimum values
             in the data over the specified range.
 WHOLE       The program is to display all of the spectrum.
 HARDCOPY    The plot is to produce a hard copy.
 AXES        Axes will be plotted.
 ERASE       The screen will be erased before the plot.
 LINES       The plot is not done as a histogram, but as
             a 'join the dots' line plot.  (Only applies
             to SPLOT.)

 User variables -    (">" input, "<" output)

 (>) SOFT    Specifies the device and type to be used for soft
             plots.  See the SOFT command for more details.
 (>) HARD    Specifies the device and type to be used for hard
             plots.  See the HARD command for more details.
 (<) TVXST   is set to the starting x-value for the plot.
 (<) TVXEN   Is set to the final x-value for the plot.
 (<) TVHIGH  Is set to the same value as HIGH.
 (<) TVLOW   Is set to the same value as LOW.
 (<) TVFILE  Is set to the value of SPECTRUM.
 (<) TVCOLOR Is set to the GRPCKG code for the plot colour.
             (The TV.. variables are intended for use by
             cursor routines, and reflect the settings for the
             last plot made, even if XSTART etc are changed.)

 (Other user variables may be set by the command processor, in
 connection with the parameter values.)

                                     KS / CIT  30th April 1984