program polint_main

real x_tab(20), y_tab(20), x_min, x_max, x_plot(200), y_plot(200)
real delta_x, dy_plot(200)
integer ntab, i, nplot, m, j, pgopen

write(*,*)'Please tell me the number of tabulated values:'
read(*,*) ntab

open(unit=10, file='input_value.dat')
do i=1,ntab
read(10,*) x_tab(i), y_tab(i)
end do

write(*,*) 'Type in min and max of x:'
read(*,*) x_min, x_max

write(*,*) 'How many points to draw ?'
read(*,*) nplot

write(*,*) 'How many point to form polynomial ?'
read(*,*) m

delta_x = (x_max - x_min) / (nplot - 1)

do i=1, nplot
x_plot(i) = x_min + (i-1) * delta_x
call locate(x_tab,ntab,x_plot(i),j)
k = min( max(j-(m-1)/2,1) , ntab+1-m )
call polint(x_tab(k), y_tab(k), m, x_plot(i), y_plot(i),
& dy_plot(i))
end do

do i=1,nplot,10
write(*,*) 'x_plot and y_plot,', x_plot(i), y_plot(i)
end do

if ( pgopen('?') .le. 0 ) stop
call pgenv(2.0, 6.0, 0.0, 40.0, 0, 1)
call pgline(nplot, x_plot, y_plot)
call pgclos