Point not match and connect with the nearest point to line

Point not match and connect with the nearest point to line

The data I exported from the ANSYS FLUENT...and when i plot it the line is not follow the black dot but connect in the zig zag direction.. Any one can fix it :(

I wish to know how to rearrange the data so that the i can match the nearest black dot to plot a line in order to erase the unwanted data

[Rik]

Isn't it possible to adjust this at the source? A first approximation is easy: sort by x-values. To clean up you might need a complex method like calculating the change of direction.

[Jan]

when i plot it the line is not follow the black dot

How do you know, which is the wanted trajectory? How is this defined mathematically? The corner at the bottom looks confusing and I'm not sure, what the wanted path is.

[TAN SAK JIE]

it cant adjust the data at the source as it only allowed transfer data from there. I have try sort by x-value, the magneta line will move in vertical zig zag line

I realised that maybe it is due to the arrangement of the x value is computed in row so the magneta line is plotted from the black dot to back dot linearly but not match the point nearest to each other to form the wanted path.

[Jan]

This is not trivial. If the point is preferred, which changes the direction of the former trajectory as small as possible, then the corner at x=0.25 will be a problem:

So you need a smart algorithm, which considers the nearest point, if it is near enough, but decides for another point, if the trajectory is straight enough. For 2D and 3D surfaces Matlab offers the alphaShape , but I do not know the command for a line.

How are the positions of the dots calculated? The creator does not know, that this is a connected graph. Otherwise it should be trivial to output the coordinates in the correct order directly.

[Image Analyst]

Are you willing to simply hand draw a dividing line through the right and left portions?

Answer 1

[Jan]

To my surprise finding the nearest point iteratively solves the problem already:

[x,y] = nearestConnection(a.Topwall(:,2), a.Topwall(:,3));
plot(x, y)

function [xa, ya, index] = nearestConnection(x, y)
xa    = zeros(size(x));
ya    = zeros(size(y));
index = zeros(size(x));

% Find the initial point defined by the smallest X value:
[~, idx0] = min(x);
xa(1)     = x(idx0);
ya(1)     = y(idx0);
index(1)  = idx0;
x(idx0)   = NaN;   % Mask original point
y(idx0)   = NaN;

for k = 2:numel(x)
   dist     = (x - xa(k - 1)) .^ 2 + (y - ya(k - 1)) .^ 2;
   [~, idx] = min(dist);
   index(k) = idx;
   xa(k)    = x(idx);
   ya(k)    = y(idx);
   x(idx)   = NaN;
   y(idx)   = NaN;
end
end