Problem in adding column in text file

Hello everyone,

I have an hdf file containing lat, lon and another parameter hp. I also have a text file that contains lat lon values along with other variables. What I want to do is read the lat lon values from text file, match/collocate them with the lat lon of hdf and extract the hp values at corresponding points (means extract the hp at lat lon of hdf). And then place these hp values in the form of column in a text file (in the same text file).

I have tried to do this in the following way but it didn't add the column in the text file. My first question is

1) Is there a way of doing this through for loop?

2) Secondly, how to add column in the text file?

Thank you.

%%   Read latitude longitude from hdf file
M_CP = hdfread('D:\MYD06_L2.A2017198.0540.061.2018034074555.hdf', 'Cloud'); 
M_lat = hdfread('D:\MYD06_L2.A2017198.0540.061.2018034074555.hdf', 'Latitude'); 
M_lon = hdfread('D:\MYD06_L2.A2017198.0540.061.2018034074555.hdf', 'Longitude'); 

lat_txt = tab.lat; 
lon_txt = tab.lon; 

lat_i = imresize(M_lat,[7570 270],'bilinear');  
lon_i = imresize(M_lon,[7570 270],'bilinear'); 

%% To match lat lon values in text file with hdf file
mask = ismembertol(lattxt, lat_i) & ismembertol(lontxt, lon_i); 
mask2 = M_CP(mask); 

%% Add column in the text file
filename = 'D:\Data.txt'; 
Data = importdata(filename);
dlmwrite('D:\TestData', [Data mask2], '%f\n');

[Walter Roberson]

What error did you encounter?

We do not have that hdf file to test with.

[Zhou Ci]

Actually it doesn't show any error.

After running the code, when I checked the text file, it was same (means column was not added to it).

I have attached csv file containing latitude, longitude and phase values from hdf file.

Answer 1

[Walter Roberson]

Note that you need to look in the new file for the new column, not the old one.

%%   Read latitude longitude from hdf file
if ispc()
    hdf_filename = 'D:\MYD06_L2.A2017198.0540.061.2018034074555.hdf';
    data_filename = 'D:\Data.txt';
    new_filename = 'D:\TestData.txt';

    M_CP = hdfread(hdf_filename', 'Cloud_Phase'); % 2030X1354 double
    M_lat = hdfread(hdf_filename, 'Latitude'); % 406x270 double
    M_lon = hdfread(hdf_filename, 'Longitude'); % 406x270 double
else
    hdf_filename = 'Hdf_Data.xlsx';
    data_filename = 'Data.txt';
    new_filename = 'TestData.txt';

    M_CP = readmatrix(hdf_filename, 'sheet', 'Phase');
    M_lat = readmatrix(hdf_filename, 'sheet','Latitude');
    M_lon = readmatrix(hdf_filename, 'sheet', 'Longitude');
end

%% Read lat lon from Text file (I imported data in the form of table (7570x28 table)). 

tab = readtable(data_filename, 'ReadVariableNames', true, 'VariableNamingRule','preserve');

lat_txt = tab.lat; % extract the column of latitude values
lon_txt = tab.lon; % extract the column of longitude values

F = scatteredInterpolant(M_lat(:), M_lon(:), M_CP(:));
mask2 = F(lat_txt, lon_txt);

%% Add column in the text file
tab.mask2 = mask2;
writetable(tab, new_filename);

[Zhou Ci]

It gives me error at this line:

Error using scatteredInterpolant
The number of data point locations should equal the number of data point values.