shortest path in 2D matrix between two coordinate points

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Sohaib Bin Altaf 2018-7-5

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回答： Sohaib Bin Altaf 2018-7-10

image.png

As in the attached image, i have a 2D matrix of 50 by 50. The matrix contains zeros (blue) and ones(yellow). Imagine it as a floor, The yellow or ones mean the walls. In this whole matrix a transmitter(T) and receiver (R) can be placed anywhere and i need to know how many walls the signal penetrates when it reaches from T to R. Lets suppose the T is at (x,y) and R is at (i,j). I take the shortest path between T and R. If i get the shortest path i can calculate the number of 1s in the path and that will be the number of walls which i need.

Can anyone help in this regard.. Thank you

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Answer 1

KSSV 2018-7-5

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YOu have the following options to check:

1. Do interpolation of the points along the path, if any point has 1, it is crossing the wall. Note that, for this you need to generate lot many points along the path so that a point lies on the yellow path.

2. Generate the points along the path, get the nearest neigboours to those points and see, any point is from yellow path.

3. Find the intersection between shortest paths and yellow paths. This would be better a solution.

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Sohaib Bin Altaf 2018-7-8

在 MATLAB Online 中打开

adnan.jpg

can you check the code below, it gives me the results, but why is the y-axis in reverse order, why it starts from top. i have used "axis xy" command but it doesn't help much... it sets the axis but the coordinates are still not plotted the way i want... i need it in the way i have shown in the picture attached to this comment... to fit into the system i am working on... May be imagesc command is the reason but i have tried surf aslo... looking forward for any help

clc

clear all

close all

M = zeros(50);

% draw lines

for x = [20,30]

    M(x,:) = 1;
end

for y = [13,25,37]

    for x = [1:20, 30:50]
        M(x,y) = 1;
    end
end

p1 = [15,25];

p2 = [33,45];

% get direction d = p1-p2;

d = d/max(abs(d)); % limit to 1 px step size

steps = 0:1:max(abs(p2-p1));

for i=length(p1):-1:1 p_line(:,i) = round(p2(i) + steps.*d(i)); end

idx = sub2ind(size(M), p_line(:,1), p_line(:,2));

walls = sum(M(idx));

M(idx) = 2;

imagesc(M)

fprintf('You passed %i walls', walls)

Sohaib Bin Altaf 2018-7-9

Yes you are right, "axis xy" command inverts the y-axis as i require but the coordinate system still does not represents the value the way i need. when i use "surf" instead of imagesc the axis are fine but the coordinate system plots it differently, like (x,y) is plotted as (y,x).

Even if i don't plot the matrix into figure, still the results are similar as if i plot an image.

Sohaib Bin Altaf 2018-7-9