MATLAB Answers


connecting every two endpoints

Asked by tarsis
on 12 Nov 2013
Latest activity Edited by Walter Roberson
on 27 Apr 2017
Hi all, I have the following formula that allow me to plot 2D points calculated from a text file.
plot(endpnts(:,1),scyendpnts,'sr', 'MarkerSize',5,'MarkerFaceColor', 'b', 'MarkerEdgeColor', 'none'); %plot all endpoints a red dots
plot(endpnts(R,1),scyendpnts(R),'sr', 'MarkerSize',5, 'MarkerFaceColor', 'b', 'MarkerEdgeColor', 'none');
I'm trying to also connect the points two by two with a line, like (4:1) with (5:1), (6:1) with (7:1) and so on but can't figure out how - by using the statement bellow I can draw a line between all points.
hold on;
plot(endpnts(:,1),scyendpnts,'LineWidth',2, 'MarkerFaceColor','b');
plot(endpnts(R,1),scyendpnts,'LineWidth',2, 'MarkerFaceColor','b')
I thank you in advance


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2 Answers

Answer by Walter Roberson
on 12 Nov 2013
 Accepted Answer

plot(endpnts(:,1),scyendpnts,'sr', 'MarkerSize',5,'MarkerFaceColor', 'b', 'MarkerEdgeColor', 'none');
is enough to draw lines between each pair of points, with red square markers.
I am not sure what more you want done? Do you want a line connecting the last point to the first? If so then
plot(endpoints([1:end 1],1), scyendpnts([1:end 1]), 'sr', 'MarkerSize',5,'MarkerFaceColor', 'b', 'MarkerEdgeColor', 'none');
Are you trying to connect every point to every other point, so point 4 is connected to point 1, 2, 3, 5, 6, etc?


on 12 Nov 2013
Hi Walter, thanks a lot.
Just one more question, is there a way for this plot start from endopoint 4 instead of 1?
Thank a lot
x = reshape(endpnts(4:end,1), 2, []);
y = reshape(scyendpnts(4:end), 2, []);
Just watch out that the number of remaining points is even (so the number of original points must be odd); if it is not then the above code will crash trying to match up the last entry.
on 13 Nov 2013
Awesome, thanks again.

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Answer by Seyedfarid Ghahari on 27 Apr 2017

Is there any automatic way to connect points to each other as 1 to 2, 3 to 4, 5 to 6, ... without using for. In other words, I have Xi, Yi, Zi and Xj, Yj, and Zj vectors which contain X, Y, and Z coordinates of start (i) and end (j) of many lines. I would like to draw these lines, but if I use:
Matlab connects all lines, while I want to have all lines disconnected!


That is what my answer above does: reshape into columns of length 2, and MATLAB will draw each column as a distinct line.
By doing this, all points are connected in series. That is, 1 is connected to 2, 2 to 3, 3 to, ... while I do not want any connection between 2 and 3 or between 4 and 5 etc. I figured it out: I used NaN at every two points;)

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