Hi Rob, Have a look at the @LOC and @WEQ transformations. There are examples of say, computing the location of the 20-degree isotherm, which might be similar to what you're thinking; you would define your variable and do a contour plot. There's also an FAQ, How can I show the value of my variable at its deepest depth? which might get you started in the right direction. -Ansley On 2/28/2011 10:26 AM, Rob Briggs wrote: Hello, I'd like to plot a transect that follows, for example, the flowline of the steepest descent of elevation. I was looking at the demos for using DDC and flowline, but they didn't really get me to my objective. All I can think of would be something as follows, which would be most unferret like, and I'm sure there might be an easier way . For example, looking at Greenland use etopo20 set region/X=80W:10W/Y=57:85 LET r1 if ROSE lt 0 then 0 else ROSE shade R1; go land ! get array of diffs LET xdiff = (-1)*R1[X=@DDC] ! negative so I can visualise downwards LET ydiff = (-1)*R1[Y=@DDC] ! plot array of vectors VECTOR/over xdiff,ydiff . I'd then like to pick a point, say max elevation, or a certain lat/lon and get the elevation transect down the path of steepest descent. I could so as follows: for points around point of interest find the max vector around this point record lat/lon/elevation of the max vector point jump to that point and set it as teh point of interest repeat loop until no more vectors to check load and plot file of elevation points But I don't know how to get to the vectors as data, not as a plot. Further question; By creating the transect I will have lost my regular grid, how could I plot the data with the lat and lon labels at each index point (or every 2 or 4 or 5)? Regards, Rob Briggs ----------------------------------------------- C4043C Department of Physics and Physical Oceanography Memorial University of Newfoundland, St. John's NL, A1B 3X7, Canada Phone : 001 (709) 864-2407 Email : rdbriggs@xxxxxx Website : http://www.physics.mun.ca/~rdbriggs/ |