Hi all, Here is another method, similar to what Hein does, but using the polymark.jnl script to draw a whole group of points at once. (see  yes? go/help polymark for details of the script.)  This method doesn't let you make each symbol a different size according to the value of the field,which Hein's method would let you do if you like.  But it's a little simpler. Because the POLYGON/LINE command does not have the range of colors that the POLYGON/FILL command does, unfilled shapes cannot represent the same range of values that filled ones do.  But perhaps using POLY/LINE/FILL for positive and POLY/FILL without the line for negative values would be a way to distinguish positive and negative differences.  I plot the whole field first, so that the color key represents all the data, then overlay just the positive values with the /LEV qualifier to use the same colors for the values of the variable, and qualifiers  /LINE/FILL to outline the polygons.    cancel region    use etopo120    palette light_centered    set window/aspect=`60/80`:axis       go basemap x=40:120 y=-20:40       ! Create lists of x and y points at all of the grid coordinates,    ! and also the function value in the region we want.       let lon = xsequence(x[gx=rose,x=40:120,y=-20:40] + 0*y[gy=rose,x=40:120,y=-20:40])    let lat = xsequence(0*x[gx=rose,x=40:120,y=-20:40] + y[gy=rose,x=40:120,y=-20:40])    let elev = xsequence(rose[x=40:120,y=-20:40])       ! Make a mask to distinguish locations of positive values       let mask = if elev ge 0 then 1       ! First draw all the points with a color key representing the whole range       go polymark poly/over/key/nolab lon, lat, elev, circle, 0.8       ! Overlay just the positive values, with /LINE/FILL to outline    ! these polygons, and /LEV to keep same color levels       go polymark poly/over/lev/line/fill/nokey/nolab mask*lon, mask*lat, elev, circle, 0.8    Hein Zelle wrote: ```Nicolas Schneider wrote: ``` ```I have 2-dimensional (x-y) data of temperature differences. I would now like to draw a 2D-plot with symbols instead of filled grid boxes (SHADE). That means that instead of a filled grid box, I would like to draw a symbol reflecting the value in that grid box. Positive temperature differences should be drawn with filled circles with the size depending on the magnitude of the temperature difference. Contrastingly, negative temperature differences should be drawn with open circles, again depending on the magnitude of the difference. Is this possible with ferret? Where should I look for? Under SHADE commands or PLOT commands? ``` ``` The following does approximately what you want. It's not very pretty, I plot the data twice to distinguish between open and closed polygons. I find it really looks better if you only use filled polygons and let the color distinguish between negative and positive, but that's up to you. Look for the POLYGON command in the ferret manual for further options and explanation. Producing a circle instead of a diamond is left as an excercise for the reader :-) Hope that helps, Hein Zelle use etopo120 set region/x=40:120 /y=-20:40 set window/aspect=`60/80`:axis palette light_centered go basemap let xdiamond = tsequence({-1,0,1,0}) let ydiamond = tsequence({-0,1,0,-1}) let size1 = if (rose gt 0) then 0.5+abs(rose/10000) else 0 let size2 = if (rose lt 0) then 0.5+abs(rose/10000) else 0 repeat /i=10:50:2 (repeat /j=26:66:2 (polygon /key /nolab /fill /levels=(-8000,8000,1000) /overlay x[g=rose]+xdiamond*size2, y[g=rose]+ydiamond*size2, rose ; ppl shaset reset)) repeat /i=10:50:2 (repeat /j=26:66:2 (polygon /key /nolab /line /levels=(-8000,8000,1000) /overlay x[g=rose]+xdiamond*size1, y[g=rose]+ydiamond*size1, rose ; ppl shaset reset)) ``` ```-----------------------------------------------------------------< ``` ``` Hein Zelle Dept. of Oceographic Research KNMI, The Netherlands work: zelle@knmi.nl http://www.knmi.nl/~zelle private: hein@icce.rug.nl http://www.icce.rug.nl/~hein Phone: +31 (0)30 2206704 ``` ```-----------------------------------------------------------------< ``` ```-------------------------------------------------------------- Zie ook/see also: http://www.knmi.nl/maildisclaimer.html ```