You can open the file directly in write mode
fh = fopen('ResultFile.txt','w');
If file already exists, this will over-write the all old contents of text file and you can write simply new contents. If the file not exist it will create a empty file. No need to manually check and delete file.
Still if you need check & delete option
if exist('ResultFile.txt', 'file')==2
delete('ResultFile.txt');
end
