program cooling_test_r
      real time(100),Temp_black(100),Temp_white(100)
      open(unit=10,file='cooling_data.txt')
      read(10,*)n
      do i=1,n
        read(10,*) time(i),Temp_black(i),Temp_white(i)
      end do
      close(10)
      dt=0.01
      write(*,*)'Initial temperature?'
      read(*,*) T_ini
      write(*,*)'Surounding temperature?'
      read(*,*) Ts
      if(pgopen('/xwin')<=0)stop
      icolor=1 
      call pgenv(time(1),time(n),20.0,100.0,0,0)
      call pgpt(n,time,Temp_black,9)
 101  write(*,*)'Cooling rate r?'
      read(*,*) r
      T=T_ini
      do i=1,10000
        T=T-r*(T-Ts)*dt
        call pgpt(1,i*dt,T,20) 
      end do
 103  write(*,*) 'Again? (1=yes,0=no)'
      read(*,*) key
      if(key==0) goto 102
      if(key/=1) goto 103
      icolor=icolor+1
      call pgsci(icolor)
      goto 101
 102  write(*,*)'your last r value is', r
      write(*,*)'Bye!'
      end