# Export followed by Import producing "0.e1" numbers

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.

• Please post a snippet of the data, so that we can try to reproduce the behavior. Aug 24 '15 at 7:00
• 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. Aug 24 '15 at 7:05
• 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"] Aug 24 '15 at 10:05
• use .m format to preserve exact precision Aug 24 '15 at 11:52
• Ah, thank you! :) That might come in handy. I've decided I'll just redo everything with 3 times the precision value, now. :P Aug 24 '15 at 12:11

List[02.7745530926768973,0.00124287564828610557236474032372086640.33865082835168153,03.1320806025128776,03.1262338523773163,0.002729727837121941666216905332743110410.3781937081269392,0.000794220121976915380972559405297512821.0511881767729303,02.9372865212434487,02.5786797291683388,03.4913067025680555,03.4050525516996344,01.7137742939876988,03.210012647512957,0.000991007316859270504655343714262016870.03446455280318874,0.001078420290055695294558732280472662610.9198460804579403,0.000285263775555151413796522996690896430.06306105024607492,02.643792350067955,01.336393802620609,01.4768850172897074,02.91781013108647,03.1781825229994505,0.001864464163594463774215524740728049840.9610361487083864,02.743632616359945]

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.