Re: Draw straight line, but display zigzag line!
- To: mathgroup at smc.vnet.net
- Subject: [mg17718] Re: Draw straight line, but display zigzag line!
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Tue, 25 May 1999 02:15:08 -0400
- References: <7hogpn$fue@smc.vnet.net> <7i33tn$bd7@smc.vnet.net> <7i7jje$e1b$2@dragonfly.wolfram.com>
- Sender: owner-wri-mathgroup at wolfram.com
<adam.smith at hillsdale.edu> wrote in message news:7i7jje$e1b$2 at dragonfly.wolfram.com... > Allan, > > I think what he means by zig-zag, is that on the screen display with > the default PlotPoints setting there is a slight "wavy-ness" to the > plot. As I pointed out in my post, it only seems to appear on the > display. Setting PlotPoints -> 2 (or a similar small number) seems to > clear up the display. Thanks Adam, Yes, I guess that it is due to the 25 points plotted by Mathematica interfering with the way the computer system tries to draw a straght line using discrete pixels - the same thing woud presumably happen with a low definition printer. Some experiments: ln1=Plot[2*x+1,{x,0,10}]; which uses Cases[ln1,Line[pts_]:> Length[pts], Infinity][[1]] 25 points is, as you say, wavier than ln2=Plot[2*x+1,{x,0,10}, PlotPoints->2]; But, interestingly, we have ln2[[1]] {{Line[{{0.00001,1.00002},{9.73608,20.4722},{9.99999,21.}}]}} compared to the "ideal" ln3 = Show[Graphics[Line[{{0,0},{10,21}}]]]; ln3[[1]] Line[{{0,0},{10,21}}] Of course, with sn=Plot[20Sin[x^2]+1,{x,0,10}]; we need to increase the points sn2=Plot[20Sin[x^2]+1,{x,0,10},PlotPoints->30]; We can combine the two approaches Plot[20Sin[x^2]+1,{x,0,10},PlotPoints->30, Epilog->Line[{{0,0},{10,21}}] ]; without needing to do something like Show[sn2,ln3]; But the last way may be unavoidable in some cases Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 > Adam Smith > In article <7i33tn$bd7 at smc.vnet.net>, > "Allan Hayes" <hay at haystack.demon.co.uk> wrote: > > > > bickel <bickel at ms17.hinet.net> wrote in message > > news:7hogpn$fue at smc.vnet.net... > > > I have a problem about drawing a straight. > > > > > > When I draw a straight ,ex: y=2x+1. > > > > > > I use Plot[2*x+1,{x,0,10}], it actually draw a line. > > > > > > But the line is like zigzag line. > > > > > > Can I do about this problem, setup some graphic option > > > > > > or ....? > > > > > > > How jagged is it? There may be a more serious problem, but the line > can only > > be as smooth as the pixel size on your screen will allow. > > > > Allan > > --------------------- > > Allan Hayes > > Mathematica Training and Consulting > > Leicester UK > > www.haystack.demon.co.uk > > hay at haystack.demon.co.uk > > Voice: +44 (0)116 271 4198 > > Fax: +44 (0)870 164 0565 > > > > > > > --== Sent via Deja.com http://www.deja.com/ ==-- > ---Share what you know. Learn what you don't.--- > > >