How manage for loop to calculate distances?
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Guilherme Weber Sampaio de Melo
am 17 Nov. 2023
Kommentiert: Dyuman Joshi
am 17 Nov. 2023
Helo,
I am trying to calculate distance in km using two variables with a set of latitude and longitude. I tried to use the "distance" funtion inside of two for loop but it is giving an error. Code is in follow:
lat= [-8, -8.2, -8.21, -8.34, -8.9];
long = [-18, -18.2, -18.3, -18.4, -18.45];
total=length(lat);
i=0;
j=0
for i=1:total
for j=1:total
i=i+1;
j=j+1;
all_distances(:,k)=distance(lat(:,i,j),long(:,i,j),lat(:,i+1,j+1),long(:,i+1,j+1),wgs84Ellipsoid("km"));
end
end
I should have a new "all_distances" variable with 5 values of distance, but it is only showing the error:
Index in position 3 exceeds array bounds (must not exceed 1).
Someone know what is the problem? Thanks in advance!
1 Kommentar
Steven Lord
am 17 Nov. 2023
Don't try to change the loop variables inside a for loop. On one hand, any changes you make will be thrown away when the next iteration of the loop starts. On the other hand, during the last iteration of the j loop you increment i and j and make j one greater than the length of lat, which seems wrong the way you're trying to use it. You're taking one step off the end of the gangplank, and MATLAB doesn't want to get wet!
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Dyuman Joshi
am 17 Nov. 2023
Bearbeitet: Dyuman Joshi
am 17 Nov. 2023
As the goal here is to find the distance between consecutive points -
%Data
lat= [-8, -8.2, -8.21, -8.34, -8.9];
long = [-18, -18.2, -18.3, -18.4, -18.45];
%Define a reference to find distance as linear distance in km
wgs84 = wgs84Ellipsoid("km");
len = distance(lat(1:end-1), long(1:end-1), lat(2:end), long(2:end), wgs84)
4 Kommentare
Dyuman Joshi
am 17 Nov. 2023
@Guilherme Weber Sampaio de Melo, I've edited my main answer. Please check it.
Weitere Antworten (1)
Torsten
am 17 Nov. 2023
Bearbeitet: Torsten
am 17 Nov. 2023
I should have a new "all_distances" variable with 5 values of distance, but it is only showing the error:
Why 5 ? You should have 4 + 3 + 2 + 1 = 10 distances if you have 5 positions.
You get a symmetric matrix distance(i,j) where distance(i,j) is the distance from position i to position j.
Maybe "pdist2" is the correct code to use in your case.
In your code, lat and long are arrays of size 1x5. So why do you suddenly use them as three-dimensional arrays in
all_distances(:,k)=distance(lat(:,i,j),long(:,i,j),lat(:,i+1,j+1),long(:,i+1,j+1),wgs84Ellipsoid("km"));
?
3 Kommentare
Dyuman Joshi
am 17 Nov. 2023
How is "distance" defined in this context?
Is there a mathematical formula you are using as a reference?
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