docs: def main():
      """
      NAME
         plotXY.py
  
      DESCRIPTION
         Makes simple X,Y plots
  
      INPUT FORMAT
         X,Y data in columns
  
      SYNTAX
         plotxy.py [command line options] 
  
      OPTIONS
          -h prints this help message
          -f FILE to set file name on command line 
          -c col1 col2 specify columns to plot
          -xsig col3  specify xsigma if desired
          -ysig col4  specify xsigma if desired
          -b xmin xmax ymin ymax, sets bounds  
          -sym SYM SIZE specify symbol to plot: default is red dots, 10 pt
          -S   don't plot the symbols
          -xlab XLAB
          -ylab YLAB
          -l  connect symbols with lines
          -fmt [svg,png,pdf,eps] specify output format, default is svg
          -sav saves plot and quits
          -poly X   plot a degree X polynomial through the data
          -skip n   Number of lines to skip before reading in data
      """
      fmt,plot='svg',0
      col1,col2=0,1
      sym,size = 'ro',50
      xlab,ylab='',''
      lines=0
      if '-h' in sys.argv:
          print(main.__doc__)
          sys.exit()
      if '-f' in sys.argv:
          ind=sys.argv.index('-f')
          file=sys.argv[ind+1]
      if '-fmt' in sys.argv:
          ind=sys.argv.index('-fmt')
          fmt=sys.argv[ind+1]
      if '-sav' in sys.argv:plot=1
      if '-c' in sys.argv:
          ind=sys.argv.index('-c')
          col1=int(sys.argv[ind+1])-1
          col2=int(sys.argv[ind+2])-1
      if '-xsig' in sys.argv:
          ind=sys.argv.index('-xsig')
          col3=int(sys.argv[ind+1])-1
      if '-ysig' in sys.argv:
          ind=sys.argv.index('-ysig')
          col4=int(sys.argv[ind+1])-1
      if '-xlab' in sys.argv:
          ind=sys.argv.index('-xlab')
          xlab=sys.argv[ind+1]
      if '-ylab' in sys.argv:
          ind=sys.argv.index('-ylab')
          ylab=sys.argv[ind+1]
      if '-b' in sys.argv:
          ind=sys.argv.index('-b')
          xmin=float(sys.argv[ind+1])
          xmax=float(sys.argv[ind+2])
          ymin=float(sys.argv[ind+3])
          ymax=float(sys.argv[ind+4])
      if '-poly' in sys.argv:
          ind=sys.argv.index('-poly')
          degr=sys.argv[ind+1]
      if '-sym' in sys.argv:
          ind=sys.argv.index('-sym')
          sym=sys.argv[ind+1]
          size=int(sys.argv[ind+2])
      if '-l' in sys.argv: lines=1
      if '-S' in sys.argv: sym=''
      skip = int(pmag.get_named_arg('-skip', default_val=0))
      X,Y=[],[]
      Xerrs,Yerrs=[],[]
      f=open(file,'r')
      for num in range(skip):
          f.readline()
      data=f.readlines()
      for line in data:
          line.replace('\n','')
          line.replace('\t',' ')
          rec=line.split()
          X.append(float(rec[col1]))
          Y.append(float(rec[col2]))
          if '-xsig' in sys.argv:Xerrs.append(float(rec[col3]))
          if '-ysig' in sys.argv:Yerrs.append(float(rec[col4]))
      if '-poly' in sys.argv:
            pylab.plot(xs,ys)
            coeffs=numpy.polyfit(X,Y,degr)
            correl=numpy.corrcoef(X,Y)**2
            polynomial=numpy.poly1d(coeffs)
            xs=numpy.linspace(numpy.min(X),numpy.max(X),10)
            ys=polynomial(xs)
            pylab.plot(xs,ys)
            print(polynomial)
            if degr=='1': print('R-square value =', '%5.4f'%(correl[0,1]))
      if sym!='':
         pylab.scatter(X,Y,marker=sym[1],c=sym[0],s=size)
      else:
         pylab.plot(X,Y)
      if '-xsig' in sys.argv and '-ysig' in sys.argv:
          pylab.errorbar(X,Y,xerr=Xerrs,yerr=Yerrs,fmt=None)
      if '-xsig' in sys.argv and '-ysig' not in sys.argv:
          pylab.errorbar(X,Y,xerr=Xerrs,fmt=None)
      if '-xsig' not in sys.argv and '-ysig' in sys.argv:
          pylab.errorbar(X,Y,yerr=Yerrs,fmt=None)
      if xlab!='':pylab.xlabel(xlab)
      if ylab!='':pylab.ylabel(ylab)
      if lines==1:pylab.plot(X,Y,'k-')
      if '-b' in sys.argv:pylab.axis([xmin,xmax,ymin,ymax])
      if plot==0:
          pylab.show()
      else:
          pylab.savefig('plotXY.'+fmt) 
          print('Figure saved as ','plotXY.'+fmt)
      sys.exit()