Loop Code Through Each Row of Excel Spreadsheet and Save Result Matrix

I haven't been on MATLAB for a while. I suppose I am very rusty. But I have a spreadsheet, and there are two columns of interest: one is labeled x_coord and the other is labeled y_coord. For each row of both columns, I am converting the x and y coordinate values to longitude and latitude degree values. Then, I am writing the results in a matrix. However, it is just not working. I am looking to have a pair of latitude and longitude values for each row, based on the x and y cooredinates. I'd greatly appreciate any help.

N=[];
for K = 1:172
    data = readtable('zipcode_information2.csv', 'PreserveVariableNames',true)
    X = data(:,ismember(data.Properties.VariableNames, {'x_coord'}))
    Y = data(:,ismember(data.Properties.VariableNames, {'y_coord'}))
    info = shapeinfo('ZIP_CODE_040114.shp');
    proj = info.CoordinateReferenceSystem;
    [lat,lon] = projinv(proj,X{i,1},Y{i,1});
    outdata = [lat,lon]
    N = [N; outdata]
    
end

writematrix(N, 'LongLat.csv',"WriteMode","append") 

Answer 1

[Cris LaPierre]

You don't need a loop. Perform the calculation on the entire column at once.

data = readtable('zipcode_information2.csv', 'PreserveVariableNames',true)
info = shapeinfo('ZIP_CODE_040114.shp');
proj = info.CoordinateReferenceSystem;
[lat,lon] = projinv(proj,data.x_coord,data.y_coord);
N = [lat,lon]

writematrix(N, 'LongLat.csv',"WriteMode","append") 

[CMatlabWold]

It is working - Thank you!

Answer 2

[M.B]

The issue is with your indexing. You declare K as the index and use i inside the loop.

I agree with Cris, you don't need a loop. The function "projinv" takes vectors as inputs. If you insist on using a loop, you can try the following:

% place all fixed parameters outside the loop  
N=nan(172, 2);
data = readtable('zipcode_information2.csv', 'PreserveVariableNames',true);
X = data(:,ismember(data.Properties.VariableNames, {'x_coord'}));
Y = data(:,ismember(data.Properties.VariableNames, {'y_coord'}));
info = shapeinfo('ZIP_CODE_040114.shp');
proj = info.CoordinateReferenceSystem;
for K = 1:172
    [lat,lon] = projinv(proj,X(K),Y(K));
    outdata = [lat,lon];
    N(K, :) = outdata;
end
writematrix(N, 'LongLat.csv',"WriteMode","append"); 

[CMatlabWold]

Thanks!