About this blog : My Ferret Plot

This blog is to share some of my experiences/tips/tricks with the scientific data visualization and analysis tool Ferret. You will also see many other helpfull computer related information on oceanographic research in this blog.
 
Ferret is a free data analysis and visualization tool primarily designed for oceanographers and meteorologists by PMEL NOAA. Ferret has its own advantages and disadvantages compared to other tools popular among earth science community like Matlab, NCL, GrADS, GMT, Python etc. In the last several years of use, i like Ferret for its simplicity and the quality of its graphics. However, Ferret is extremely disappointing in terms of serious data analysis due to its "delayed mode evaluation" (ie. all expressions are evaluated only when Ferret sees an action command like "plot"). For this reason I use Matlab/Fortran for data analysis and Ferret is mainly reserved for generating graphics. However, there are situations where Ferret can be quite handy, if you know how to use it properly (a good example is finding climatology from a time series, Ferret could do that in few lines of script). I will share some of my experience/trips/tricks with Ferret through this blog.

You can find all my posts in the Ferret email forum here (search for my name "Jaison Kurian").

Here is a nice Ferret plot using enhanced shading intervals for smoother colors and data filling to remove data gaps near land boundary. Please see the script used for generating this figure below.



\ cancel mode verify      set data levitus_climatology ! load data      let temp_fln = temp[d=1,k=1,i=@FLN:15,j=@FLN:15] ! Linear interpolation to fill gaps                                           ! between data & land boundary      let temp_fill = temp_fln[j=@FNR] ! additional filling using nearest neighbor      define symbol flev = "(-inf)(-2,20,1)(20.5,29,0.5)(inf)" ! fill levels      define symbol clv = "(28,28,1)" ! cont levels      define symbol hl = 20.5:379.5:30 ! hlimits      define symbol vl = -89.5:89.5:20 ! vlimits      define symbol pal = rainbow2_cmyk.spk ! palette      ppl axlint 2,1 ! axis label interval      ppl axnmtc 1,1 ! axis minor tics      ppl axlsze 0.112,0.112 ! axis label size      ppl color 6,73,73,73 ! new color      fill/pal=($pal)/lev=($flev)/hlim=($hl)/vlim=($vl)/nolab temp_fill      contour/ov/nolab/lev=($clv)/spacing=1.5/size=0.115/color=1 temp_fill      plot/vs/line/color=6/nolab/ov {20.5,379.5},{0,0} ! draw equator-line      go fland 20 black ! fill land      label `(379.5+20.5)/2`,95,0,0,0.18 @C001 Sea Surface Temperature (^oC) : Levitus Climatology      ! frame/file=sst_gbl.gif ! uncomment for gif outpu