Hi Arpita, You don't need the step where you regrid with @MOD, unless your data is on a different calendar definition as mentioned in the FAQ on modulo regridding; or if you were starting with monthly data on a monthly axis that was not centered on the middle of the month, as mentioned in the Users Guide which talks about handling shifts due to differences between linear and modulo regridding. If you just define Then you can plot them together or subtract the two series.let sst1n=sst1[gt=myt@mod] let sst2n=sst2[gt=myt@mod] Ansley There's no risk of On 6/14/2010 8:31 PM, Arpita Shetty wrote: Hello ferret users, I have SST data for 12 years from 1998 to 2009. I need to extract data for the month of may from each of these years and plot them for comparison. This is what i tried: define axis/t/t=1-may:31-may:1/units=days myt let sst1=sst[x=@ave,y=@ave,t=1-may-1998:31-may-1998] let sst2=sst[x=@ave,y=@ave,t=1-may-1999:31-may-1999] !regridding to myt axis & eliminating shift of data due to @mod transformation let sst1n=sst1[gt=myt@asn] let sst2n=sst2[gt=myt@asn] plot/vlim=28.5:31.5 sst1n[gt=myt@mod] plot/vlim=28.5:31.5/ov sst2n[gt=myt@mod] The problem is, this works perfectly for variable sst1. But the corresponding values for sst2 and so on are marked as zero. Could you pls help me out with this? |