sl - Make a slice through an image and plot the results       RWW & MWP 


sl 10,-2 -4,6			Generate the data along a slice between the
				two points (10,-2) and (-4,6) in image 1 and i
	                        write it in the file 'slice' in your home 

sl h:-2,2 v:1,5	ps:4		Make the slice but force the horizontal and
				vertical scales to the specified limits. 
				Normally sl autoscales based on the extrema
				of the data. Use plot symbol 4 (crosses) 
				instead of a line.

sl im:2 ovl: lt:0 add:3         Generate the data along the previous slice. Use
                                image 2, overlay the plot on the previous 
				plot using a dotted line. Add 3 to the y-values.

cr 2;sl x(0),y(0) x(1),y(1) fn:"slice1"
				Make the slice, but use the cursor to
				define the points.  (If using a tek4014 window
				in a 5620 see the note in 'da ?!'.)  The data 
				will be put in the file slice1 in the current
				directory. This is similar to the macro 'slli'
				in .GMACROS.

sl logy: fn:"/dev/null"		make the plot using the logarithm of the image, 
			        but don't write a file.

sl im:2 m: fact:1E4		Add an additional column from image 2 to an
				existing slice file.  Scale the data by 10000.
				Note you can only merge once, since slice 
				assumes the existing file has four columns.


Sl will produce a plot of the values at the points in an image along a slice.
The default is a linear-linear plot but linear-log plot is also possible 
(this does not affect the printed output described below.) Line types as 
described in "fl" are available.

The normal execution writes out four columns for each point, suitable for
plotting with mongo or some other package.  The first two are the x and y offset
positions relative to the center of the map (in map units).  The third is the
distance from the first point and the fourth is the map value at that
point.  An example follows:

14       -9        0     0.5162
13       -8     1.41      1.043
12       -8     2.24      1.474
11       -7     3.61      1.583
10       -7     4.47      2.169
 9       -6     5.83      2.109
 8       -6     6.71      3.088
 7       -5     8.06      4.641
 6       -5     8.94      5

Running sl again into the same file with the merge (m:) option but with
another image will add another column of data.  For each position in
the existing file the value of the closest grid point of the new image
will be used.  This will work best if the two images have the same
gridding. A copy of the original file (before merging) is kept in 
"file".old (e.g., slice.old).

Each data value is multiplied by the scale factor.  This is useful
since mongo doesn't scale data or to correct a map for beam efficiency,


'slli' is a macro in .GMACROS which will generate a slice along a
line between two cursor points.

This document was last updated on Tue Oct 17 16:24:05 EDT 2000 by Marc W. Pound.