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This is probably an easy question to answer, but I need a fresh eye... I'm struggling with processing the following file (extract shown here) It's a list of dates, and positive/negative time durations formatted using "m" and "s".

Apr-09 -1m 47s
Apr-11 -1m 15s
Apr-12 -0m 59s
Apr-13 -0m 44s
Apr-14 -0m 28s
Apr-15 -0m 13s
Apr-16 0m 1s
Apr-17 0m 15s
Apr-18 0m 29s
Apr-19 0m 42s
Apr-20 0m 55s
Apr-21 1m 8s

I'm reading the file in OK:

d = ReadList["/tmp/data.txt", 
  {Word, Number, Character, Number, Character}];

and assembling the pieces using this:

d /. {s_String, m_Integer, _, n_Integer, _} :> {s, 
   N@If[m >= 0, (60 m + n)/60, (60 m - n)/60]}

which appears to work:

{"Apr-09", -1.78333}, 
{"Apr-11", -1.25},
{"Apr-12", 0.983333}, 
{"Apr-13", 0.733333}, 
{"Apr-14", 0.466667}, 
{"Apr-15", 0.216667},  
{"Apr-16", 0.0166667}, 
{"Apr-17", 0.25}, 
{"Apr-18", 0.483333},  
{"Apr-19", 0.7}, 
{"Apr-20", 0.916667}, 
{"Apr-21", 1.13333}

but then I noticed that the 0s lost their signs on import, so the conversion is inaccurate: 

d

{{"Apr-09", -1, "m", 47, "s"}, 
 {"Apr-11", -1, "m", 15, "s"},
 {"Apr-12", 0, "m", 59, "s"}, 
 {"Apr-13", 0, "m", 44, "s"}, 
 {"Apr-14", 0, "m", 28, "s"},
 {"Apr-15", 0, "m", 13, "s"},
 {"Apr-16", 0, "m", 1, "s"},
 {"Apr-17", 0, "m", 15, "s"},
 {"Apr-18", 0, "m", 29, "s"}, 
 {"Apr-19", 0, "m", 42, "s"}, 
 {"Apr-20", 0, "m", 55, "s"},
 {"Apr-21", 1, "m", 8, "s"}}

plot

The problem is that ReadList's Number reads "-0" as "0". Is there a better way of reading in data like this? I tried using Sign but unfortunately Sign[-0] gives 0... :)

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  • $\begingroup$ Would you show the data as imported, before you manipulate it? I suspect that the number -0 is already read in as 0. If you read in "-0" as a string, you should be able to retain the minus sign. $\endgroup$
    – DavidC
    Commented May 1, 2013 at 12:37
  • $\begingroup$ @DavidCarraher Yes, the -0 is converted to 0 by ReadList. I could try reading as Word, I suppose. But the problem is then moved elsewhere rather than solved... $\endgroup$
    – cormullion
    Commented May 1, 2013 at 12:45

1 Answer 1

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ReadList thinks your file has lists of 4, not 5, elements; it views the minutes and the "m" as a single element. The following will import the lists. 

dd = ReadList["/tmp/data8.txt", {Word, Word, Number, Character}]

{{"Apr-09", "-1m", 47, "s"}, {"Apr-11", "-1m", 15, "s"}, {"Apr-12", "-0m", 59, "s"}, {"Apr-13", "-0m", 44, "s"}, {"Apr-14", "-0m", 28, "s"}, {"Apr-15", "-0m", 13, "s"}, {"Apr-16", "0m", 1, "s"}, {"Apr-17", "0m", 15, "s"}, {"Apr-18", "0m", 29, "s"}, {"Apr-19", "0m", 42, "s"}, {"Apr-20", "0m", 55, "s"}, {"Apr-21", "1m", 8, "s"}, {"Apr-22", "1m", 20, "s"}, {"Apr-23", "1m", 32, "s"}, {"Apr-24", "1m", 43, "s"}, {"Apr-25", "1m", 54, "s"}, {"Apr-26", "2m", 4, "s"}, {"Apr-27", "2m", 14, "s"}, {"Apr-28", "2m", 23, "s"}, {"Apr-29", "2m", 32, "s"}, {"Apr-30", "2m", 41, "s"}}

The following displays the output in minutes.

dd /. {s_, m_String, n_Integer, _} :> {s, (ToExpression[StringDrop[m, -1]]*60
+ (If[StringTake[m, 1] == "-", -1, 1]) n)/60}

DateListPlot[%]

plot

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  • $\begingroup$ Cool, thanks, once I've got the input in the right format, I'm there. I'm still stuck trying to get ReadList working for me to get to that point... $\endgroup$
    – cormullion
    Commented May 1, 2013 at 13:31
  • $\begingroup$ If you post a link to your data file, others may be able to help with the importing via ReadList. $\endgroup$
    – DavidC
    Commented May 1, 2013 at 14:23
  • $\begingroup$ The first gray box is an actual extract from the file, so it should be easy to save this in a text file. $\endgroup$
    – cormullion
    Commented May 1, 2013 at 14:36
  • $\begingroup$ The output in the first gray box is already transformed by Mathematica. Cutting and pasting it does not provide a list. I could try to guess how the data looked in the file form, but I prefer to review the actual file. $\endgroup$
    – DavidC
    Commented May 1, 2013 at 15:21
  • $\begingroup$ Thanks for sending the file. It turns out that ReadList parses the input differently from what I had imagined. (see second attempt, above.) $\endgroup$
    – DavidC
    Commented May 1, 2013 at 15:50

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