Number of points that passes a line

The attached data contains x and y values. Assuming they are walking in 1 direction per axis i.e. some people move from left to right thus x always increases, other people move from south to north. How can I find the number of people who passes a certain line? i.e. min(x)= -4, max(x)= 4, I want to find the number of people who passes my line x(from -4 to 0) y(0).

Answer 1

[KSSV]

You can calculate the intersection points of your (x,y) data and the given line. To find the intersection points you can use this file exchange: https://in.mathworks.com/matlabcentral/fileexchange/22441-curve-intersections

Let L1 be your (x,y) walking data and L2 be your line data.

P = InterX(L1,L2) ; 

Your L1, L2 should be row matrices of size 2*m and 2*n. Where first row corresponds to x and second row correspond to y. The number of points P, you got is what you want.

[Abdulkarim Almukdad]

Can you please help me further, first, its not neccessary that my data points will match my line for example someone might go from y= -0.5 to y = 0.5 thus he didn't step on the 0 line, will this be an issue or this equation will count him as 1 ? also can you please give further explination on what is 2*m and 2*n? did you mean that 2 is 2 rows ? lastly, how can I convert my table data to a single row ? I think I can do it by for loop, but is there any other eaiser way or function? Thanks a lot in advance

[KSSV]

I have seen your data..it has 178*27 matrix....If you have (x,y) pairs it should be having a even number of columns. And your max and min x-value is huge i.e [ -627.88 524.25]. When I try to use interX, with the lines [-4 to +4] , I am not getting any intersection points, But if you extend this line to say -800 to +800, you will get some intersection points. Check the below:

num = xlsread("01) 90.xlsx") ;

num(:,3) = [] ;   % some extra column present, so remove it 

x = num(:,1:2:end) ;
y = num(:,2:2:end) ; 

x = x(:) ; 
y = y(:) ; 

L1 = [x' ; y'] ;
m = 100 ; 
L2 = [linspace(-800,800,m); zeros(1,m)] ; 

P = InterX(L1,L2) ; 

plot(x,y,'r')
hold on
plot(L2(1,:),L2(2,:),'b')
plot(P(1,:),P(2,:),'*k')

[Abdulkarim Almukdad]

Thanks a lot KSSV, that was very helpful.