Thanks a lot to Kevin W., for his comment in my previous post.
Corrgram, it a nice package and I found very nice information to understand it a little bit better on Internet apart from the R help page.
I worked with it for a while and the plots are very nice and useful.
This is one of them with the Demo data for the fish meal parameters (previous posts).
You can choose other options. The links I wrote give you good details.