I'm going to assume that you're entering them into excel by trusting that
format long
will reveal the entire number. It won't really. You can get more digits other ways, though be aware that when changing base, you're not assured that the result actually can be represented in a finite number of digits. At some point, the results you get will just be junk.
load QuestionWorkspace
fprintf('%.18f\n',Data1)
fprintf('%.18f\n',Data2)
We can see that the numbers are definitely not the same, but if you had copied them from the console window using the formatting you'd used before, then you're reducing the precision enough that they are the same.
Alternatively, please consider that I haven't used Excel in a decade, and I don't use the modern tools for writing to xlsx files. If for some reason, the data were converted to single precision floats, then you'd lose enough precision that the numbers would indeed become equal.
