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Re: export to file with a specific precision

  • To: mathgroup at smc.vnet.net
  • Subject: [mg111520] Re: export to file with a specific precision
  • From: Albert Retey <awnl at gmx-topmail.de>
  • Date: Wed, 4 Aug 2010 05:48:24 -0400 (EDT)
  • References: <i38rhl$d6m$1@smc.vnet.net>

Hi,

> 
> I need to export to a file several numbers with a specific number of
> digits on the right of the decimal. I'm trying this with the function
> NumberForm[] and Export[] but the problem is that export function is
> not exporting only the number but the full inputform. For example, if
> I do this:
> 
> Export["teste.dat", NumberForm[1.23456, {3, 4}]]
> 
> it will write in the file this:
> 
> NumberForm[1.23456, {3, 4}]
> 
> It happens the same with:
> 
> NumberForm[1.23456, {3, 4}]>>"teste.dat".
> 
> Another problem is that in the end I need the data in fortran form,
> which mean I can't pass to a string before exporting because for the
> cases of raw data that are in scientific format the final result will
> be a string with "10^x" which is not fortran format.

Actually I think that converting to String is what you want in this
case, note that you can use ToString together with NumberForm or
FortranForm:

ExportString[ToString at NumberForm[1.23456, {3, 4}], "Table"]

ExportString[ToString at FortranForm[1.23456*10^-8], "Table"]

should both work. If you need 4 digits and the fortran like e notation
you could do something like this:

ExportString[ToString at NumberForm[1.23456*10^-8, {3, 4},
   NumberPadding -> {"", "0"},
   NumberFormat -> (If[#3 === "", #1, Row[{#1, "e", #3}]] &)
   ], "Table"]

Note: Export with a filename exports the result of ExportString to a
filename, so you can use ExportString as a convenient way to see what
Export would do.

hth,

albert




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