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Re: hold question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg132337] Re: hold question
  • From: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>
  • Date: Wed, 12 Feb 2014 05:13:30 -0500 (EST)
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Dear Group:

Manipulating and importing/exporting dates is always a pain in the neck, in any of the languages I am aware of.
Mathematica has functions to work around many of these issues, and I was actually able to complete the task
I was involved in, but even then there is an issue I obviously do not understand.

Say I have this date in an Excel sheet: 01/08/2007. I import in into Mathematica.  I want to prevent it from becoming an arithmetical expression, so
I sorround it by Unevaluated, HoldAll, and other hold-like devices, but I do not obtain the desired result. The date becomes a division.
For example, the output of HoldComplete[2+2] is  HoldComplete[2+2] , but instead the output of HoldComplete[ 01/08/2007]
is HoldComplete[1/(8x 2007)].

What I am overlooking?
(Mathematica 9.0)



Hi, Francisco,

No need to use Hold or alike. I created the Excel file with the name "dateExample.xls". It only contains the date, the one  you wish: 1/8/2007. Then I imported it into the notebook that was in the same directory as the Excel file as follows:

imp=Import[NotebookDirectory[]<>"dateExample.xls"]

This the outcome:

{{{{2007,1,8,0,0,0.}}}}

Then this:

DateString[
 imp[[1, 1, 1]], {"", "", "Month", "/", "Day", "/", "YearShort"}]

yields the desired output:

"01/08/07"

It appears as a string and, therefore, is not considered by Mathematica as an arithmetic operation.

Have fun,

Alexei




Alexei BOULBITCH, Dr., habil.
IEE S.A.
ZAE Weiergewan,
11, rue Edmond Reuter,
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Office phone :  +352-2454-2566
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e-mail: alexei.boulbitch at iee.lu





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