MEDUSA-Training-How-to-run-MEDUSA-1D-(-on-NOC-linux-system).md

@@ -408,11 +408,26 @@ to see them easily, you can use `ferret`:
 module load ferret
 ferret
 ```
-if ferret is not available, you can log on another linux-machine like `theia`. To use ferret, just :      
+if ferret is not available, you can log on another linux-machine like `theia` (open another linux session, log on theia: `ssh -Y theia` and go to your running directory, where your outputs are) . To use ferret, just :      
 ``` sh
 use $file_name
 show data ## to see the data
 shade var[k=1,l=1]
 ```
-here i plot the surface of a 3D variable (k=1) and if there are several time record, l=1 ask to plot the first
-i'll show you more on the training, but if you're used to matlab or python, do not hesitate to use your own thing ;)
\ No newline at end of file
+Here i plot the surface of a 3D variable (k=1) and if there are several time record, l=1 ask to plot the first
+i'll show you more on the training, but if you're used to matlab or python, do not hesitate to use your own thing ;)   
+
+
+If you want to compare 2 outputs with ferret:    
+load both files, and check the data with `show data`. you now have 2 data sets. you can specify to which dataset you refer to with [d=...] like we just did for the vertical layer or time.  here is an example :    
+```sh
+use $file1
+use $file2
+show data ## to see the data
+shade din[k=1,l=1, d=1] !! File1's DIN
+set w 2 !! open a new window
+shade din[k=1,l=1, d=2] !! File2's DIN
+set w 3 !! 3rd window 
+shade/lev=(-inf)(-10,10,0.5)(inf)/pal=white_centered din[k=1,l=1, d=2]-din[k=1,l=1, d=1]
+!!just plot the diff, with a diff colorbar, and setting the colorbar limits
+```