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MathGroup Archive 2005

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Re: How to read a data file in text format?_from a new learner

  • To: mathgroup at smc.vnet.net
  • Subject: [mg62414] Re: How to read a data file in text format?_from a new learner
  • From: Bill Rowe <readnewsciv at earthlink.net>
  • Date: Wed, 23 Nov 2005 01:13:19 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

On 11/22/05 at 4:42 AM, readnewsciv at earthlink.net (Bill Rowe) wrote:

>On 11/21/05 at 3:54 AM, yanshanguke at 163.com (deepthinker) wrote:

>>I want to import a data file that produced by spectrometer into
>>mathemathica and fit the data. The file is in text format
>>("data.txt"). The data in the file is characters: first line:some
>>descriptions. second line: 200, 45.5. third line: 201,44.3. and so
>>on. If you open the file "data.txt", you will see: 

>>transmission ratio by UV-3150
>>200, 45.5
>>201,44.3
>>202,44.6
>>203,46.7
>>....
>>1,000,75.5
>>1,000,76.3

>>How to import these data in to mathematica 5.0 and plot the figure?

>Probably the simplest way to deal with this file would be to use
>Import. That is:

>data=Cases[Import["data.txt", "CSV"], {_?NumberQ,_?NumberQ}];
>ListPlot[data];

>Should do what you want.

In looking over my comments above, I realized I made an assumption that may not be valid.

In possing the problem a comma character appears to be used in two distinct ways, as a field separator and as a separator within a number to improve readability. If the file literally has this format, there will be no simple/easy way to read the data into Mathematica or any other program for that matter.

The point is if a comma is interpreted as a field separator, then the line

1,000,75.3 

will be seen as three numbers 1, 0, and 75.3. But if the comma is interpreted as part of a number this line is likely to be interpreted as 100075.3, a single number.

When I suggested using Import I assumed this line would actually appear in the file as

1000,75.5

That is the comma will always be a field separator which is how it would be treated by Import.
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