how to preallocate a table in matlab for for loop to read multiple excel sheet

Here I modified a code from here to read a multiple excel sheets from a file. However, I do not know how to preallocate the empy table created since my variable 'Data' keep changing size for every loop iteration?

filename ='2012hf.xlsx';
[~,SheetNames]  = xlsfinfo(filename);
nSheets = length(SheetNames);
VarNames ={'Day15','Day16','Day18','Day19'};
Data=table();
for ii=1:nSheets
    Name=SheetNames{ii};
    VarName=VarNames{ii};
    Data=[Data, readtable(filename,'Sheet', Name,'Range','F1:F97')];
    Data.Properties.VariableNames{'cmufc_HF'} = VarName;
end
S.Data=Data

Answer 1

[Image Analyst]

You can either not worry about it (it may not speed things up or down that much), or else you can allocate way more than you need and set the remaining unused rows to null to crop them off.