With the axes and frame in place, SINE
is ready to draw the sine curve. The sinewave
routine calculates
the x and y positions for two cycles and plots them on the screen:
! SINEWAVE - This subroutine calculates and plots a sine wave.
SUBROUTINE sinewave( )
USE DFLIB
INTEGER(2) dummy, newx, newy, locx, locy, i
INTEGER(4) color
REAL rad
EXTERNAL newx, newy
PARAMETER ( PI = 3.14159 )
!
! Calculate each position and display it on the screen.
color = #0000FF ! red
!
DO i = 0, 999, 3
rad = -SIN( PI * i / 250.0 )
locx = newx( i )
locy = newy( INT2( rad * 250.0 ) )
dummy = SETPIXELRGB( locx, locy, color )
END DO
END SUBROUTINE
SETPIXELRGB takes the two location parameters, locx and locy, and sets the pixel at that position with the specified color value (red).