How to use textscan for multiple variables

Hello,

I am currently working on a project where i import a gpxfile without gpxread, and sort the data into variables (elevation, longitude, etc.).

However, my code keeps bringing up empty matrixes for my variables.

Any help would be appreciated!

filename = input('Open file: ', 's');
[fileID, errmsg]= fopen(filename);
if (fileID==-1)
    disp(errmsg)
end
a=importdata(filename);
d=char(a)

~feof(fileID)
Latitude = textscan(d,'<trkpt lat="%f" lon="%f">\n');
for Longitude = textscan(d, 'long="%f">\n');
    for Elevation = textscan(d, '<ele>%f</ele>)\n');
        for Time = textscan (d, '<time>2020-02-01T%f3z</time>\n');
        end
    end
end
fgetl(chr);

Answer 1

[Walter Roberson]

a=importdata(filename);
d=char(a)

Okay, so d is a character vector or character array -- in particular, d is not a file id. You did [fileID, errmsg]= fopen(filename); but you never use the fileID other than to check feof() once on it and discard the results of the check.

Latitude = textscan(d,'<trkpt lat="%f" lon="%f">\n');

You are passing the characters in d to textscan. It is valid for textscan purposes if d is a 2D array of characters: textscan will take the characters in linear index order in such a case (which would read along columns, not across rows).

textscan() will skip leading whitespace in most cases, and then will try to literally match what is in d against '<' 't' 'r' k' 'p' 't' and so on in consecutive positions. If the first non-whitespace does not match the literal characters <trkpt lat=" then textscan() will stop reading and return empty. textscan() never searches through the text looking for matching places: it always starts at the current position and tries to match the next format item. The current position for a character array is the beginning of the array.

for Longitude = textscan(d, 'long="%f">\n');

Reminder that when textscan() works, it returns a cell array of values. If textscan() were able to find multiple occurances of that pattern in a row, with there being only one % format, it would return a cell array that contained a single entry, and the single entry would be a numeric column vector.

You would be on better grounds if you were reading from a file instead of from a character array, but you would be much better off using something like regexp() to parse the text.

Given the structure of the file, possibly you could use xmlread() or readstruct()