# program to read in data from a file
# and plot it

# read in a multi coloumn data file

from pylab import *
import matplotlib.pyplot as plt


# read in MV, B-V, and temp of main sequence stars from colrmag.dat
MV,BV,temp=loadtxt('colormag.dat',unpack=True,skiprows=4,usecols=(0,1,2))

# plot the data MV versus B-V

plt.plot(BV,MV,'b*',label='My Plot')
plt.xlabel('B-V')
plt.ylabel('Apparent mag.')
axis([-0.4,3,18,-5]) # set range on axis
plt.annotate('my label',(1,4))


# read in orion data
num,s,V,BmV=loadtxt('OrionUBV.dat',unpack=True,skiprows=4,usecols=(0,1,2,3))

# overplot orion data
plt.plot(BmV,V,'ro')

# adjust the data to match the theoretical main sequence for d=400 
# distance in pc
d=100 # try 100 pc distance
dm=5.*np.log10(d/10)
magV=V-dm

# deredden and extinct the data if desired 
#AV=0.1 # extinction at V band in magnitudes
#R=3.1 # ratio of extinction to reddening
#EBMV=AV/3.1 # this is teh excess B-V called E(B-V)
# deredmagV=magV+AV
# deredmagBmV=BV+EBMV
#magBmV=BmV-EBMV

show()

# now print out a new file with only the magnitudes of each star
from astropy.io import ascii
ascii.write([magV,magBmV], 'newdata.dat', names=['V mag.', 'B-V color'])