Hello, Your data is organized as lists of longitude, latitude, time and measurements. You used a good method, plot/vs/ribbon, to visualize the density and range of the data. yes? go basemap x=15:120 y=-60:30 yes? plot/vs/over/nolab/ribbon/thick/size=0.08/symbol=17/key/LEV= v LON,LAT,SWHCOR To interpolate it to a grid, use one of the SCAT2GRID functions    yes? show function scat2grid*xy Perhaps the scat2gridgauss_xy function. A note on the syntax: in your axis definition, the latitude axis should be one of these: DEFINE AXIS/Y=60S:30N:10/UNIT=DEGREES ylat DEFINE AXIS/Y=-60:30:10/UNIT=DEGREES ylat Not -60S.  -Ansley On 2/3/2014 7:49 PM, Selvam G. wrote: ```Dear Prof, I would like to know the ferret command for linear Interpolation. I am dealing with Ifremer altimeter wave data for Indian Ocean.I plotted the map but when the Interpolation command is given the .des file is not shown as it is Interpolated. I am attaching one of my wave data for your consideration. I request your guidance for this Interpolation. Thanks & regards Selvam G. ----- Original Message ----- From: "Russ Fiedler" To: "ferret users" Sent: Tuesday, February 4, 2014 3:16:38 AM Subject: Re: [ferret_users] Spatial Trend The time units for the trend should correspond to the time axis for your data. If it's days then you will have to multiply by 365 or 365.25 to get the trend in terms of years. Russ On 03/02/14 23:45, iwlod@xxxxxxxxxxxxxxxxxxx wrote: ``` ```I dont think it is that simple - units on slope are way to small can someone else confirm? thanks ``` ```Simply shade slope. Sent from my iPhone ``` ```On Jan 31, 2014, at 4:17 AM, iwlod@xxxxxxxxxxxxxxxxxxx wrote: Collective Ferret Wisdom :-) How do I go from a linear regression line plot (with go regresst) to a SPATIAL (lat x lon) trend map of say, temperature for the past 20 years? Thank you ```