Exporting kml file of lines

I am working on exporting kml file with series of coordinates which are joined together but I keep receiving this error? How can I solve this??

??? Error using ==> kmlwrite>addData at 665
Function KMLWRITE expected its second input, S or ADDRESS,
to be one of these types:

struct, char, or string cell array

Instead its type was double

Error in ==> kmlwrite at 193
addData(kmlDoc, numDataArgs, dataArgs, options, userSupplied);

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My Code

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M = xlsread('YCKMap.xlsx');
waypoints =[M(:,2), M(:,3)];
[lttrk,lntrk] = track('rh',waypoints,'degrees');
figure(),geoshow(lttrk,lntrk,'DisplayType','line', 'color','r');
filename = '560620.kml';
kmlwrite(filename, lttrk,lntrk);