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How to avoid the rounding error, when exporting data like this:

ra = Range[0.004, 0.074, 0.0005];
Export["range.txt", ra]

The result is this: enter image description here

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  • $\begingroup$ Why? When you read this data with another program that uses floating point, the error will grow back anyway. $\endgroup$
    – John Doty
    Commented Jun 28, 2018 at 11:24
  • $\begingroup$ This is just an example, but it inflates the size of my files unnecessarily. As I am handling a huge amount of data I have to figure out some efficiency. $\endgroup$
    – Kay
    Commented Jun 28, 2018 at 11:56
  • $\begingroup$ Try something like ToString@NumberForm[#, {10, 4}] & /@ ra before exporting. Does that help? $\endgroup$
    – halirutan
    Commented Jun 28, 2018 at 12:02
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    $\begingroup$ Alternatively to @halirutan's suggestion, you can use Export["range.txt", NumberForm[ra, {10, 4}], "List"] $\endgroup$
    – Lukas Lang
    Commented Jun 28, 2018 at 12:39
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    $\begingroup$ but it inflates the size of my files unnecessarily If size is an issue why are you not writing binary files ? Not only will that ensmallen your files, it will circumvent the problem which prompted your question, and make reading/writing faster. Win win win. $\endgroup$
    – High Performance Mark
    Commented Jun 29, 2018 at 5:57

1 Answer 1

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You may use SetPrecision on your list, ra.

ExportString[SetPrecision[ra, 6], "Table"]

0.004
0.0045
0.005
0.0055
0.006
0.0065
0.007
0.0075
0.008
0.0085
0.009
0.0095
0.01
0.0105
...

Hope this helps.

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