MATLAB: Find “intersection” of data array

dataset interpolate intersection

Hello everybody,
I would like to find the "intersections" of different data arrays. The arrays look similar this:
x=[0 1.2 2.5 3.4 4.6 5.4 6.8 7.3 8.6 9.8 7.1 8.5 9.9 10.1 11.4]
y=[100 90 80 70 65 60 55 50 45 40 40 42 44 52 62]
I would like to cut off the part under the intersection and redefine the data set. So it would be enough to find the two connection points (in this example (8.6;45) and (9.9;44)). Any ideas, how to do this? I have ran out of ideas and really need new ideas/inspiration from you guys!
Cheers, Christian

Best Answer

Download and use selfintersect:
https://www.mathworks.com/matlabcentral/fileexchange/13351-fast-and-robust-self-intersections
I tried it on your example values:
>> x = [0,1.2,2.5,3.4,4.6,5.4,6.8,7.3,8.6,9.8,7.1,8.5,9.9,10.1,11.4];
>> y = [100,90,80,70,65,60,55,50,45,40,40,42,44,52,62];
>> [~,~,s] = selfintersect(x,y)
s =
    9   12
>> xnew = x([1:s(1),1+s(2):end])
xnew =
    0.00000    1.20000    2.50000    3.40000    4.60000    5.40000    6.80000    7.30000    8.60000    9.90000   10.10000   11.40000
>> ynew = y([1:s(1),1+s(2):end])
ynew =
   100    90    80    70    65    60    55    50    45    44    52    62
>> plot(x,y,'-*',xnew,ynew,'-*')
If you have multiple intersects you will have to use a loop (or some alternative) to process each row of the output matrix s.
Related Question