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I often have data in the form of

 YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 1950 -1.022 -1.146 -1.289 -1.058 -1.419 -1.36 -1.334 -1.05 -0.578 -0.395 -1.151 -1.248 1951 -1.068 -1.196 -1.208 -0.437 -0.273 0.48 0.747 0.858 0.776 0.75 0.729 0.466 1952 0.406 0.131 0.086 0.262 -0.267 -0.634 -0.231 -0.156 0.362 0.309 -0.34 -0.124 1953 0.024 0.379 0.263 0.712 0.84 0.241 0.416 0.253 0.524 0.092 0.049 0.314 -0.093 -0.312 and so on ...

I want to convert this into time/value tuples of the type that can be easily plotted using DateListPlot. I have written some very hackish code that does the job, but it feels messy and unsatisfactory. Does anyone know of an elegant 'Mathematica' way to do this?

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    $\begingroup$ Where do you have that data? In a text file? $\endgroup$ Commented Jan 30, 2014 at 1:26
  • $\begingroup$ Yes. The original data is here - esrl.noaa.gov/psd/enso/mei/table.html I copy/paste it and get rid or the garbage at top. Make CSV in Excel and load into Mathematica. But it's just an example. I have many others, usually financial data. $\endgroup$ Commented Jan 30, 2014 at 1:36

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Here's what I came up with...

data = {{"YEAR" , "JAN", "FEB", "MAR", "APR", "MAY" , "JUN" , "JUL", "AUG", "SEP" , "OCT", "NOV" , "DEC"}, {1950, -1.022, -1.146, -1.289, -1.058, -1.419, -1.36, -1.334, -1.05, -0.578, -0.395, -1.151, -1.248}, {1951, -1.068, -1.196, -1.208, -0.437, -0.273, 0.48, 0.747, 0.858, 0.776, 0.75, 0.729, 0.466}, {1952, 0.406, 0.131, 0.086, 0.262, -0.267, -0.634, -0.231, -0.156, 0.362, 0.309, -0.34, -0.124}, {1953, 0.024 , 0.379, 0.263, 0.712, 0.84, 0.241, 0.416, 0.253, 0.524, 0.092, 0.049, 0.314}};

Since the data is arranged per month, we can build the dates as such...

Thread[{#[[1]], Range[12]}] & /@ Rest@data

Now, we can Transpose in the data and plot away...

Transpose[{Thread[{#[[1]], Range[12]}], Rest@#}] & /@ Rest@data DateListPlot[%, Joined->True]

enter image description here

You can also plot as one series by using Flatten at level 1.

DateListPlot[ Flatten[Transpose[{Thread[{#[[1]], Range[12]}], Rest@#}] & /@ Rest@data, 1], Joined -> True]

enter image description here

UPDATE

Just saw where the actual data is located which can be imported:

data = Cases[ Import["http://www.esrl.noaa.gov/psd/enso/mei/table.html", "Table"], {_?NumberQ, __}];

enter image description here

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  • $\begingroup$ That looks pretty good. I was thinking about 'Thread', but I'm not experienced with it and my first attempts didn't work. $\endgroup$ Commented Jan 30, 2014 at 1:40
  • $\begingroup$ Great! Love the addition of the import from scratch. Thanks. $\endgroup$ Commented Jan 30, 2014 at 1:45
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I'll assume your data is on file (named datas.txt) as you suggested in your comment. Then:

data = ReadList["datas.txt", Word, RecordLists -> True]

Gives

{{"YEAR", "JAN", "FEB", "MAR", "APR", "MAY", "JUN", "JUL", "AUG", "SEP", "OCT", "NOV", "DEC"}, {"1950", "-1.022", "-1.146", "-1.289", "-1.058", "-1.419", "-1.36", "-1.334", "-1.05", "-0.578", "-0.395", "-1.151", "-1.248"}, {"1951", "-1.068", "-1.196", "-1.208", "-0.437", "-0.273", "0.48", "0.747", "0.858", "0.776", "0.75", "0.729", "0.466"}, {"1952", "0.406", "0.131", "0.086", "0.262", "-0.267", "-0.634", "-0.231", "-0.156", "0.362", "0.309", "-0.34", "-0.124"}, {"1953", "0.024", "0.379", "0.263", "0.712", "0.84", "0.241", "0.416", "0.253", "0.524", "0.092", "0.049", "0.314"}}

Now, very crude, but I had to approach this differently from kale's elegant method:

 pl = Table[{StringJoin[data[[1, #]], " ", data[[k, 1]]], ToExpression[data[[k, #]]]} & /@ Range[2, 13], {k, 2, Length@data}]

Finally,

DateListPlot[pl, Joined -> True, PlotStyle -> Thick]

Mathematica graphics

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  • $\begingroup$ +1 for the ReadList function, which I wasn't aware of. $\endgroup$ Commented Jan 30, 2014 at 18:07
  • $\begingroup$ @IanSchumacher. Thanks. Also, note that for very large data, ReadList is much faster than Import $\endgroup$ Commented Jan 30, 2014 at 18:09