Unable to import matplotlib in PyDev
Sounds like the interpreter you setup for Pydev is not pointing to the appropriate version of python (that you've install mpl and np).  In the terminal, it's likely the effect of typing python is tantamount to env python; pydev might not be using this interpreter.  
But, if the pydev interpreter is pointed to the right location, you might simply have to rehash the interpreter (basically, set it up again) to have mpl show up.
You could try this in the terminal and see if the results are different:
python -c 'import platform; print platform.python_version()'
${PYTHONPATH}/python -c 'import platform; print platform.python_version()'
I am using Ubuntu 10.04 and have successfully configured PyDev to work with Python and have written a few simple example projects. Now I am trying to incorporate numpy and matplotlib. I have gotten numpy installed and within PyDev I did not need to alter any paths, etc., and after the installation of numpy I was automatically able to import numpy with no problem. However, following the same procedure with matplotlib hasn't worked. If I run Python from the command line, then import matplotlib works just fine. But within PyDev, I just get the standard error where it can't locate matplotlib when I try import matplotlib.
Since numpy didn't require any alteration of the PYTHONPATH, I feel that neither should matplotlib, so can anyone help me figure out why matplotlib isn't accessible from within my existing project while numpy is? Thanks for any help.