I am not too sure, what you are asking.
The command for a line plot (or more generally graphing a variable with just one dimensions) is just: plot
I am assuming that you would want to average over a region for this. Then you need one of the maths operators to average. If ferret can understand your data in lat lon then you could say:
for example and this should plot the average of the variable sst over the region lon=150-180E , lat=20-50N, against the third dimension assuming sst is a variable with three dimensions, and ferret can understand the dimensions in the data file called lon and lat - if it is netcdf there is a good chance, if not you have to put sst on a grid yourself.
I hope this is a start; the user guide will tell you more - as always.
From: owner-ferret_users@xxxxxxxx [owner-ferret_users@xxxxxxxx] on behalf of Nitin Patil [nitinpatil85@xxxxxxxxx]
Sent: 05 September 2015 04:25
Subject: [ferret_users] trend of SST
Dear Ferret users,
I am using HadISST dataset for SST. I have to plot trend of SST (for 30 years). Did anyone knows how to plot in ferret? It will be great help!
Thanks in advance.