New point calculation - for loop

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em_++ 2021-6-14

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https://ww2.mathworks.cn/matlabcentral/answers/855695-new-point-calculation-for-loop

评论： em_++ 2021-6-14

Hi there!

Ive got a question regarding new point calculation... So i got 2 Points (Latitude,Longitude) and I want to calculate 7198 new points between those two... So because there are so many i wanted to use a for loop.

so first step is to calculate the direction angle (this one i did get correct)
then calculate the distance between the points with pythagoras : 2700
new array s = zeros(7200,1) where i want to put the previously (2.) calculated distances ++
for loop:

for j = 1:7200

s(j,1) = distance ++; <- Here is the problem

end

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Answer 1

Scott MacKenzie 2021-6-14

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编辑：Scott MacKenzie 2021-6-14

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No need for a loop:

% arbitrary point for beginning (perhaps longitude)
x1 = randi([1 1000],1);
y1 = randi([1 1000],1);
% arbitrary point for ending (perhaps latitude)
x2 = randi([1 1000],1);
y2 = randi([1 1000],1);
n = 7200; % number of points from beginning to ending
pf = polyfit([x1 x2], [y1 y2], 1);
x = linspace(x1, x2, n);
y = polyval(pf,x);

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Scott MacKenzie 2021-6-14

在 MATLAB Online 中打开

Hmm, yes, I see. There are ways to shorten this, but I think the code below achiveves what you are looking for. I'm adding the variable m and the term "trip" for each of your 50 beginning-ending points.

m = 50; % number of trips
% example x-y values for beginnings of m trips
x1 = randi([1 1000],1,m);
y1 = randi([1 1000],1,m);
% example x-y values for corresponding trip endings
x2 = randi([1 1000],1,m);
y2 = randi([1 1000],1,m);
n = 7200; % number of points for each trip
tripPath = zeros(m,n,2); % x-y points for m trips, n points each
for i=1:m
    pf = polyfit([x1(i) x2(i)], [y1(i) y2(i)], 1);
    x = linspace(x1(i), x2(i), n); % x points for ith trip
    y = polyval(pf,x); % y points for ith trip  
    tripPath(m,:,1) = x;
    tripPath(m,:,2) = y;
end

The matrix tripPath is a mxnx2 matrix. The first dimension is for the trip (1 to m), the second dimension organizes the points for the trip (1 to n), with the 3rd dimension holding the actual x (1) and y (2) points for the trips.

em_++ 2021-6-14