real function interp(x)                                                 
        real x                                                                  
        common /pawc/nwpaw,ixpawc,ihbook,ixhigz,ixkuip,ifence(5),               
     &               lmain(8),q(500000)                                         
        call kuvect('x',ixlo,ixhi)                                              
        call kuvect('y',iylo,iyhi)                                              
        do ix=ixlo,ixhi                                                         
          if (q(ix).gt.x) goto 1                                                
        end do                                                                  
1       if (ix.le.ixlo) then                                                    
          interp = q(iylo)                                                      
        else if (ix.gt.ixhi) then                                               
          interp = q(iylo+ixhi-ixlo)                                            
        else                                                                    
          iy = ix + iylo-ixlo                                                   
          frac = (x - q(ix-1))/(q(ix) - q(ix-1))                                
          interp = q(iy)*frac + q(iy-1)*(1-frac)                                
        end if                                                                  
        return                                                                  
        end