Syntax for loop to compute distance from a fix point
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Hello Everyone,
I am working on a for loop that will compute distance a long a line from a fixed point reference associated with a lat and lon. I have a table of lat and lons, but when I attempt to run the loop the code is only computing the first distance and not running for each value in the lat and lon column. I have noticed that how I am calling the individual values of 'Full_profile_1999' table seem to be wrong but I cannot figure out how to properly call them. If anyone one could assist me with fixing the code so it runs for all then that would be great.
Note: The first few lines load, and concatenate the files together so they are one flight profile of lat and lons. These are then converted to degree and I am attempting to run them through a haversine function I made that uses the points. The problem is in the for loop, variable definition or function part of the code
Data_1 = readtable('Data_19990519_01_014_151949.csv'); %Was shortened in
Data_2 = readtable('Data_19990519_01_015_153633.csv');
Full_profile_1999 = [Data_1; Data_2];
Full_profile_1999.Distance = zeros(742, 1);
Full_profile_1999.LAT = deg2rad(Full_profile_1999.LAT);
Full_profile_1999.LON = deg2rad(Full_profile_1999.LON);
lat_ref = min(Full_profile_1999.LAT(:,1));
lon_ref = min(Full_profile_1999.LON(:,1));
% dlat = Full_profile_1999.LAT - lat_1;
% dlon = Full_profile_1999.LON - lon_1;
len = length(Full_profile_1999.LAT);
for k = 1:len
lat_2 = Full_profile_1999.LAT(k,1);
lon_2 = Full_profile_1999.LON(k,1);
haversine(lat_2, lat_ref, lon_2, lon_ref);
Full_profile_1999.Distance = dist(k);
end
function [dist] = haversine(lat_2, lat_ref, lon_2, lon_ref)
dlat = lat_2 - lat_ref;
dlon = lon_2 - lon_ref;
a = (sin(dlat/2).^2 + cos(lat_ref).*cos(lat_2).*sin(dlon/2).^2);
dist = asin(sqrt(a));
end
1 个评论
Walter Roberson
2019-7-31
Remember that length() does not necessarily refer to the first dimension: it refers to the largest dimension. If you are iterating over rows then you should be using len = size(Full_profile_1999.LAT,1)
采纳的回答
Walter Roberson
2019-7-31
编辑：Walter Roberson
2019-7-31
len = size(Full_profile_1999.LAT, 1);
for k = 1:len
lat_2 = Full_profile_1999.LAT(k,1);
lon_2 = Full_profile_1999.LON(k,1);
dist = haversine(lat_2, lat_ref, lon_2, lon_ref);
Full_profile_1999.Distance(k) = dist;
end
Or simply no loop and
Full_profile_1999.Distance = haversine(Full_profile_1999.LAT, lat_ref, Full_profile_1999.LON, long_ref);
which will work because haversine() is vectorized.
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