Is there a command line tool for data visualization and analysis?

Here's one way you could make one. Input files should be formatted with one or more columns of data. If there are two or more columns, the first column is used as the X in an X,Y plot.

#! /usr/bin/env python

import sys
import matplotlib.pyplot as pyplot

for filename in sys.argv[1:]:
   with open(filename,'rt') as sf:
      table = []
      for line in sf: table.append( [float(val) for val in line.split()] )
      table = [ row for row in table if len(row) ] ## remove empty rows
      if len(table[0]) == 1 : pyplot.plot( [y[0] for y in table ] )
      for x in xrange(1,len(table[0])): pyplot.plot( [ y[0] for y in table ], [ y[x] for y in table ] )
pyplot.show()