Dynamic Plotting "Phantom" Line

2 次查看（过去 30 天）
Chris Berry
Chris Berry 2011-4-28
Dear fellow MATLAB Users,
I have created a dynamic plotting system to be used with various x and y data points and have unwanted line appearing at the start of the plotting sequence. Here is my code as it currently stands:
__________ CODE START __________
x=[0;6;2;8;4;10;6;12;8];
y=[0;2;4;6;8;10;12;14;16];
t=numel(x);
r=x(t);
nnn=y(t);
s1=subplot(1,1,1);
set(s1,'xlim',[1 numel(x)],'ylim',sort([0 r]),'nextplot','add')
p1=plot(r,nnn,'r-');
p2=plot(r,nnn,'g*');
axis([0 20 0 20])
set(gca,'ydir','rev')
for t=1:numel(x)
r=x(t);
nnn=y(t);
set(p1,'xdata',[get(p1,'xdata') r],'ydata',[get(p1,'ydata') nnn])
set(p2,'xdata',r,'ydata',nnn)
pause(.5)
end
__________ CODE END __________
Notice how there is a line extending from the origin, to the final data point. I cannot understand why this is occurring, nor what to do to remedy it. Any help that could be lent to solve this issue would be greatly appreciated.
Thank you,
~ Chris
  2 个评论
Jan
Jan 2011-4-28
Please use the code formatting as described at the link called "Markup" on this page.
Chris Berry
Chris Berry 2011-4-28
I apologize, I am not able to find the "Markup" link on this page, nor through a site search. Would you please provide me with a link so that I can better submit questions and answers? Thanks.

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采纳的回答

Paulo Silva
Paulo Silva 2011-4-28
Initialize p1 with this code
p1=plot(nan,nan,'r-');
instead of
p1=plot(r,nnn,'r-');
  1 个评论
Chris Berry
Chris Berry 2011-4-28
Exactly! Thank you, Paulo, for your help. It is people like you that make this forum great!

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更多回答（1 个）

Jan
Jan 2011-4-28
You get a connection from the origin to the last data point, because your program explicitely instructs that.
x = [0;6;2;8;4;10;6;12;8];
y = [0;2;4;6;8;10;12;14;16];
t = numel(x);
r = x(t);
nnn = y(t);
s1 = axes('xlim',[0, 20],'ylim',sort([0 20]), ...
'nextplot','add', 'ydir','rev');
p1 = plot(r, nnn, 'r-');
p2 = plot(r, nnn, 'g*');
% Now [p1] is the last data point
for t = 1:numel(x)
r = x(t);
nnn = y(t);
set(p1, 'xdata',[get(p1,'xdata') r], ...
'ydata',[get(p1,'ydata') nnn])
set(p2, 'xdata',r, 'ydata',nnn)
pause(.5)
% In the first iteration the origin is added to [p1]!!!
end
I cannot guess, what you want to do instead. Perhaps you want to start your t-loop from 2 or remove the zeros from x and y.
  2 个评论
Jan
Jan 2011-4-28
Puh, the latency is cruel for me. I've typed the answer and waited 13 minutes until it appears completely in the web interface. Therefore I did not see Paulo's answer before.
Chris Berry
Chris Berry 2011-4-28
Ha. I still appreciate you trying to help me. Take care.
~ Chris

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