graph_tutorial.bas

 nomainwin 
 global winW, winH, xmin, xmax, ymin, ymax 
 open "test" for graphics_nsb_nf as #gr 
 #gr "trapclose [quit]" 
 #gr "down" 
 
 #gr "home" 
 #gr "posxy w h" 
 winW=2*w: winH=2*h 
 'f(x)=1.5*x^2-2*sin(5*x), x in [-2,3] 
 xmin=-2: xmax=3 
 
 nPoints=winW 'we have only this much screen dots in X range 
 dx=(xmax-xmin)/nPoints 'so this will be step in math coordinates 
 
 'now, to get ymin, ymax we have to loop 
 ymin=f(xmin) 
 ymax=ymin 
 for x=xmin to xmax step dx 
 y=f(x) 
 if ymin > y then ymin = y 
 if ymax < y then ymax = y 
 next 
 
 'now we just - plot function. Note same loop 
 #gr "color red" 
 #gr "size 3" 
 y=f(xmin) 
 #gr "set ";sx(xmin);" ";sy(y) 'just set first dot 
 for x=xmin to xmax step dx 
 y=f(x) 
 #gr "goto ";sx(x);" ";sy(y) 'then connect dots 
 next 
 
 'and finally, add axis 
 #gr "color black" 
 #gr "size 1" 
 #gr "line ";sx(xmin);" ";sy(0);" ";sx(xmax);" ";sy(0) 
 #gr "line ";sx(0);" ";sy(ymin);" ";sx(0);" ";sy(ymax) 
 
 'labeling 
 #gr "place ";sx(0)+5;" ";sy(0)-5 
 #gr "\0,0" 
 #gr "place ";sx(xmax)-20;" ";sy(0)-5 
 #gr "\X" 
 #gr "place ";sx(0)+5;" ";sy(ymax)+20 
 #gr "\Y" 
 
 #gr "flush" 
 #gr, "getbmp drawing 1 1 ";winW;" ";winH 
 bmpsave "drawing", "graph.bmp" 
 
 wait 
 
 [quit] 
 close #gr 
 end 
 
 '"any" function. You can change it as you like 
 function f(x) 
 f=1.5*x^2-2*sin(5*x) 
 end function 
 
 'To translate X from interval [a,b] to [c,d] we'll do (X-a)/(b-a)*(d-c)+c. 
 'create two functions: sx(x) and sy(y) 
 function sx(x) 
 sx=(x-xmin)/(xmax-xmin)*winW 
 end function 
 function sy(y) 
 sy=winH-(y-ymin)/(ymax-ymin)*winH 'Y is inverted, so winH-... 
 end function