How to writetable to file with 2nd row containing VariableUnits?

9 vues (au cours des 30 derniers jours)
Miguel Aznar
Miguel Aznar le 13 Nov 2017
Commenté : Jan Kappen le 22 Oct 2024
Hi Everyone,
I would like to know how to write a table to file including the metadata (specifically VariableUnits). the function " writetable " does not seem to allow for this function. I have tried to writ table to a comma delimited file and use dlmwrite (....'-append') but this adds the unit row at the bottom of the file and one character at the time instead of the entire string. I would like to have it in the 2nd row, right underneath the variable names.
  3 commentaires
Voss
Voss le 22 Oct 2024
Déplacé(e) : Voss le 22 Oct 2024
t = table([1;2;3],[4;5;6]);
t.Properties.VariableNames = {'A','B'};
t.Properties.VariableUnits = {'m','ft'};
filename = 'file.txt';
writetable_with_units_line(t,filename)
type(filename)
A,B m,ft 1,4 2,5 3,6
writetable_with_units_in_brackets(t,filename)
type(filename)
A[m],B[ft] 1,4 2,5 3,6
function writetable_with_units_line(t,filename)
fid = fopen(filename,'w');
str1 = strjoin(t.Properties.VariableNames,',');
str2 = strjoin(t.Properties.VariableUnits,',');
fprintf(fid,'%s\n%s',str1,str2);
fclose(fid);
writetable(t,filename,'WriteMode','append','WriteVariableNames',false,'Delimiter',',');
end
function writetable_with_units_in_brackets(t,filename)
fid = fopen(filename,'w');
str = strjoin(t.Properties.VariableNames+"["+t.Properties.VariableUnits+"]",',');
fprintf(fid,'%s',str);
fclose(fid);
writetable(t,filename,'WriteMode','append','WriteVariableNames',false,'Delimiter',',');
end
Jan Kappen
Jan Kappen le 22 Oct 2024
Thanks for that proposal. Yeah it can be done this way, but I'd prefer not to write my own function for that ;)
BTW, I think you can make it shorter without using fopen and friends...
function writetable_with_units_in_brackets(T, filename)
arguments
T table
filename (1,1) string
end
namesWithUnits = T.Properties.VariableNames + " (" + T.Properties.VariableUnits + ")";
T.Properties.VariableNames = namesWithUnits;
writetable(T, filename, Delimiter=",");
end
But again - no function would be better.
A solution could be an extended version of the table class, adding a property WriteVariableUnits which gets parsed during writetable. But since table can't be subclassed that will never happen :(

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Miguel Aznar
Miguel Aznar le 13 Nov 2017
I found a work around it. It is pretty simple. I hope it helps whoever is stuck trying to do the same. Write first the header with fprinf indicating %s as the formatting of your cell array. Do not forgwt the break in the last cell "\n", and indicate the metadata of your table (i.e. Table.Properties.VariableNames {1,1:end})
fid = fopen('test.csv','w')
fprintf('test.csv', '%s, %s, %s, %s, %s, %s\n', Table.Properties.VariableNames{1,1:end});
fprintf('test.csv', '%s, %s, %s, %s, %s, %s\n', Table.Properties.VariableUnits{1,1:end});
M = table2array(Table);
dlmwrite('test.csv', M, '-append') ;

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