CODEWITHSUNDEEP
matlabclassbuilt-in
Daniel
Daniel

Reputation: 27

writetable Matlab (appendtable?)

If you have a table class "T"

T = 

Var1      Var2      Var3    Var4 
____    ________    ____    _____

M       45    45    'NY'    true 
F       41    32    'CA'    false
M       40    34    'MA'    false

And you want to write the values in a file you could use, for instance:

writetable(T,'myData.txt','Delimiter', ...)

But this will delete all the information you had in myData.txt . I was wondering if there is an append function for table, or some way write without remove the old content of myData.txt.

So, Image:

type myData.txt

Hello

writetable(T, ...)

type myData.txt

Hello

Var1 Var2 Var3 Var4 

M       45    45    'NY'    true 
F       41    32    'CA'    false
M       40    34    'MA'    false

Upvotes: 2

Views: 7441

Answers (2)

ses
ses

Reputation: 128

Bob's answer is perfect for small tables. For large tables, to avoid the for loop, I recommend writing the second table to a second file, and then you can merge the files. Here is code for that:

writetable(T1,'data_01.csv');
writetable(T2,'data_02.csv','WriteVariableNames',false);

you don't want to have the variable names on the second file so that you can merge the files perfectly to a new file. If you are on Linux you can simply do:

cat data_*.csv >> data.csv

And, yet if the tables are very big, I would recommend using 'datastore'. Here is a code for that:

writetable(T1,'data_01.csv');
writetable(T2,'data_02.csv');

here we should keep the variableNames in the second file as well, so the datastore function can read the files properly:

ds = datastore('data_*.csv');

then, you can read slice by slice using 'read' function or read completely using 'readall' function, depending on your need. Please, check the documentations for that.

Upvotes: 2

Bob Mortimer
Bob Mortimer

Reputation: 459

One way is to write to the file using fopen(). Create the table:

LastName = {'Smith';'Johnson';'Williams';'Jones';'Brown'};
Age = [38;43;38;40;49];
Height = [71;69;64;67;64];
Weight = [176;163;131;133;119];
T = table(LastName,Age,Height,Weight)

Write the file:

writetable(T,'table.csv')

Open the file again:

fid = fopen('table.csv','a')

Write out the table a second time:

fmt = varfun(@(x) class(x),T,'OutputFormat','cell');
fmt(strcmp(fmt,'double'))={'%g'};
fmt(strcmp(fmt,'cell'))={'%s'};
fmt=[strjoin(fmt,',') '\n']
for r=1:size(T,1)
  x=table2cell(T(r,:));
  fprintf(fid,fmt,x{:});
end
fclose(fid);

Upvotes: 2

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