sp - Make a scatter plot comparing two images RWW & MWP
sp 1,2,1 Make a scatter plot of image 2 vs image 1 within
area 1. The results will be in the file "scatter"
in your home directory.
sp an:3 fn:"scatter3" yfact:1E-4 minx:.5
Make a scatter plot with file named scatter3 in the
current directory using area 3 multiplying the
y values by 3 and suppressing data with x < .5
sp logx: logy: miny:0 minx:0
Make a log-log plot of the images suppressing negative
sp ps:2 fill: ovl: Plot with filled triangles instead of dots and overlay
on the current scatter plot. See 'gm ?!' for a list of
plot symbols and their figure numbers. See also note on
plot symbols below.
Sp will produce a plot comparing two images using comb graphics.
The default is a linear-linear plot with dots as symbols. Log-linear and
log-log plots are also possible (this does not affect the printed output
described below.) Other symbols as described in "gm ?!" are also available.
Sp produces a four column file suitable for plotting with mongo or
other package. The four columns are x and y offsets from the image
center, the x image value, and the y image value. The points will all
be from within the specified area. The beginning of such a file
-11 -21 0.3192 2.6e-07
-10 -21 0.3849 2.571e-07
-9 -21 0.3784 2.483e-07
-8 -21 0.4007 2.424e-07
-7 -21 0.4447 2.306e-07
-6 -21 0.3818 2.189e-07
After making the graph, the integral of both images over the area is
shown on the standard output. The value shown is the sum of the points
times the area (in steradians) represented by each point in the map, e.g.:
Integral in x image is 0.000106336 [K-KM/S]*[SR] over 3.59618e-05 SR
Integral in y image is 7.77671e-12 [W/M2/SR]*[SR] over 3.59618e-05 SR
The integral is multiplied by the scale factor for that image.
Note for an integral with units [JY/BEAM]*[SR], you must divide
by the beam area in SR to get total JY. (Hint: use that number for
the scale factor.)
bmsr in .GMACROS will print out the beam area in steradians given
a FWHM in arcsec.
A NOTE ON PLOT SYMBOLS:
A list of figures and corresponding numbers is listed at the end
of "gm ?!". If the given figure width and height (fw:, fh:) are
zero (which is the initial value the first time you use "sp"),
then comb will scale them to the plot. Otherwise, the previous
value is used so that overlay plots (ovl:) come out looking nice.
So if you want comb to re-compute the plot symbol sizes, just
give "fh:0" and "fw:0".
This document was last updated on
Tue Oct 17 16:24:05 EDT 2000
by Marc W. Pound.