Alternative function or tool instead of plot or line ?

2016 4 8
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更新时间：2016 4 9
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function for drawing segment between three points in set of points (to make triangle that capture all other set of point inside it) but without using plot or line function any other function because those two function not draw at accurate coordinates ?
note / those set of points are random in x,y coordinates, and the three points i denote it like stars.
appreciate any help and i will be thankful.
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Adam
Adam 2016-4-8
What do you mean by "don't draw at accurate coordinates". Plot and line will plot at the points you tell them to, no more, no less, especially when there are no issues of very very small numbers that could cause accuracy issues
Redwan Dan
Redwan Dan 2016-4-8
i mean by that please if you take a look on image i upload with question you will see three stars in different color the two stars far away i increase value of maximum x and decrease value of y coordinates so when i try to plot between them is not draw correct segment if you can check lines in image .. thanks for answer too
Rick Rosson
Rick Rosson 2016-4-8
编辑：Rick Rosson 2016-4-8
Please post your MATLAB code. All of the code necessary so that we can reproduce the exact same plot. Thanks.
Adam
Adam 2016-4-8
编辑：Adam 2016-4-8
I don't have to time to look through carefully, but you need to check your maths and put breakpoints in at the points you are about to plot and check whether your p1, p2, p0 values are correct.
It is almost certain that it is your maths to create those points that is wrong, not the plot function.
As an aside for better code understandability and to hopefully produce fewer bugs though I would not recommend embedding maths directly in the call to scatter. Create your data first and store it, then call scatter on that data. Then the points you need to plot should be points within that stored data rather than you having to try to apply the same maths for the end points of the line that you already did when calling scatter.
Redwan Dan
Redwan Dan 2016-4-8
编辑：Walter Roberson 2016-4-9
% define values
a = [17 14 2 15 16 12 17 8 12 10; 13 1 12 12 9 6 14 8 9 10 ];
for j=1:10
if(a(1,j)==a(1,p)&a(2,j)==a(2,q))
scatter(a(1,j),a(2,j),'*')
else
scatter(a(1,j),a(2,j),'o')
hold on
end
end
p0=[a(1,7),a(2,7)]
scatter(xmax(1)+5,ylow-10,'*')
px = (xmax(1)+5)
py =(ylow-10)
p1= [px,py]
scatter(xlow-10,ymax,'*')
ppx = (xlow-10)
ppy = ymax
p2=[ppx,ppy]
plot(p1,p2)
plot(p1,p0)
plot(p2,p0)
% plot([px,py],[ppx,ppy])
% plot([px,py],p0)
% plot([a(1,p),a(1,q)],[ppx,ppy])
% line([a(1,p),a(1,q)],[a(1,6),a(2,6)])

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Ced
Ced 2016-4-8
编辑：Ced 2016-4-8

1 个投票

Hi
I think you misunderstood the plot function. The first argument are all the x values, and the second argument are all the y values. What you are plotting with plot(p1,p2) is actually ( p1(x), p2(x) ) and (p1(y), p2(y)), which is not what you want.
In this case plot should be
plot([ px ppx ],[py ppy])
The same goes for the line function, which is probably why it seemed to return garbage. The syntax is
line([ x1 x2 ],[ y1 y2 ]); % NOT line([ x1 y1 ],[ x2 y2 ])!
Your max computation does not make much sense to me. Every time you find a new maximum, you write it to xmax(l+1) (which is xmax(2)), but then compare xmax again? There is a max function... why not use it?
And yes, please paste the complete code (as in text copy-paste, not as in picture paste) in your questions so that people can run the code and actually try to see what's wrong.

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Redwan Dan
Redwan Dan 2016-4-8
thanks a lot appreciate it works correctly ^_^
Redwan Dan
Redwan Dan 2016-4-8
编辑：Redwan Dan 2016-4-8
px0 = a(1,7)
py0=a(2,7)
plot([ px ppx ],[py ppy])
plot([px0 px],[py0 py])
plot([px0 ppx],[py0 ppy])

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