PROGRAM sig2pl
*************************************************************************
* Conversion of sigma to plasmafrequency using sum-rule                 *
* the standard input file must have the format x (cm-1) sig1 (Ohm-1cm-1)*
* The outputfile comes as: x plasmafrequency**2 (cm-2).                 *
*************************************************************************
      REAL X(100000),sig(100000),sum,pi,step,nup
      INTEGER I,mm
      pi=4.*atan(1.)    
      mm=100000 
      do 10 i=1,mm                                                  
       READ(*,*,END=11) X(i),sig(i)
10    continue
      sum=0   
11    mm=i-1
      do 25 i=1,mm-1
       step=x(i+1)-x(i)
       sum=sum+step*(sig(i)+sig(i+1))/(2*0.0333795)
       nup=0
       if (sum.gt.0) nup=sqrt(4*sum/pi)
       write(*,*) x(i+1),nup*nup
25    continue
      END