I had a large table of data that I exported, and then when it had completed, I exported it to a file. (Just in the form Export["filename.dat", data], no specified format.). When I imported it later, I was confused by how much of it was 0's. Opening up the table, I saw the following chunks of data:

0.000999315368 0.00103971193 ... 0.001184 0.00112 0.00116 ... 0.0008 0.0007 0.e-3 ... 0. 0.e1 0.e1 0.e1 0.e2

Can anyone explain what this 0.e-3 format means? Why did my data export this way? The original was entirely nonzero.

  • $\begingroup$ Please post a snippet of the data, so that we can try to reproduce the behavior. $\endgroup$
    – Jason B.
    Commented Aug 24, 2015 at 7:00
  • $\begingroup$ I will if/when I can, but it was the result of a very long computation that will take a while to reproduce (a day or so of running; 12GB of RAM usage). Similar calculations with different parameters hadn't caused this behavior, either, so I wouldn't know how to get a minimal example case. I'll have to re-run the calculation anyway to get the data, so at that point I can post it here. Until then, I was hoping someone knew what sorts of values could produce the above output. $\endgroup$ Commented Aug 24, 2015 at 7:05
  • $\begingroup$ I can't at first glance reproduce 0.e-3 or similar. I suspect it has to do with some floating point precision issues. In general, x.yyy e z (spaces inserted for clarity) means x.yyy*10^z. Exporting a number like 0.00000005 would result in 5.e-8 though. As for Import issues, it may help to specify the format of the data being imported, e.g. Import["filename.dat", "Table"] $\endgroup$
    – LLlAMnYP
    Commented Aug 24, 2015 at 10:05
  • $\begingroup$ use .m format to preserve exact precision $\endgroup$
    – george2079
    Commented Aug 24, 2015 at 11:52
  • $\begingroup$ Ah, thank you! :) That might come in handy. I've decided I'll just redo everything with 3 times the precision value, now. :P $\endgroup$ Commented Aug 24, 2015 at 12:11

1 Answer 1


It turned out to be, as LLIAMNnYP suggested, a precision issue. The data I had contained values such as (in FullForm)


where -- today I learned! -- the numbers after the double-backticks indicate uncertainty in the value. When it has this much uncertainty, the number itself renders as 0.*10^-4, etc. When exported these became 0.eN, when imported these were just a normal 0.0.

  • $\begingroup$ Always +1 for self-answers $\endgroup$
    – LLlAMnYP
    Commented Aug 24, 2015 at 14:01

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