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MathGroup Archive 2007

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Re: Bad imports of data files -- extra empty lists showing up?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg80700] Re: Bad imports of data files -- extra empty lists showing up?
  • From: dh <dh at metrohm.ch>
  • Date: Wed, 29 Aug 2007 04:18:27 -0400 (EDT)
  • References: <far9ul$4dl$1@smc.vnet.net>


Hi Curtis,

have you checked that your files do not contain any invisible (control) 

characters?



Daniel



Curtis Osterhoudt wrote:

> Hi, all, 

> 

>    I noticed this problem the other day, on different data sets, not 

> thinking much of it. Then, when it cropped up again, I started to get 

> worried. I'm really not sure how to think about it, and so am requesting some 

> advice from the experts. I have tried rewriting this message a few times, and 

> can't figure out how to state the problem very clearly, so please bear with 

> me.

> 

>     I know that attachments aren't allowed, but my problem is that if I 

> copy-and-paste the troublesome dataset into this message (I've tried), 

> whatever formatting is causing the problem is lost. For example, I'll paste 

> the data into this message, then copy it from the message to a text file, 

> then save that and import it into Mathematica. The problem disappears. So if 

> anyone is curious, perhaps they can email me directly and I can send some 

> sample "bad" datasets.

> 

>    The data was taken using a VB program on a windows machine, and this 

> version of Mathematica is running on a linux machine. However, 1) the problem 

> crops up in perhaps 10 - 25% of the files so far, ALL of which were 

> originally produced on a windows machine; 2) the problem does not occur in 

> the same place in each file, IF it occurs at all; 3) if I re-do the import, 

> and the file imports incorrectly, the problems occur at the same places in 

> the file; 4) if I remove portions of the file (using a text editor, perhaps), 

> the problems may occur in different spots, or the problems may disappear. 

> 

>    What I've tried:

>          Import the data sets using Import["file name", "Table"]. Typically 

> the datasets have ".txt" or ".dat" extensions. Some files consist of number 

> triplets; some of doublets; they're all TAB-separated.

>     Expected behavior: the data is imported correctly; files with n lines of m 

> numbers per line should show up as tables consisting of n length-m lists. 

> This is what happens most of the time.

>     Actual behavior: A given file will import correctly, but with occasional 

> empty lists interspersed in among the data points. For example, a 2*10^5 

> length dataset has empty lists ( {} ) at seven different places in it. A 10^4 

> length dataset has only one empty list. 

> 

>    So far, I've just been importing the datasets, searching for lines which do 

> not contain the expected doublets or triplets, and just deleting those lines. 

> But that's obviously extra work (even if Mathematica does it for me). I've 

> been able to cut some of these example data files down a bit, and still 

> retain the "bad" behavior. If anyone can shed some light on this for me, I'd 

> much appreciate it!

> 

> 




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