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MathGroup Archive 2011

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Difficulty with patterns

  • To: mathgroup at smc.vnet.net
  • Subject: [mg122281] Difficulty with patterns
  • From: "McHale, Paul" <Paul.McHale at excelitas.com>
  • Date: Sun, 23 Oct 2011 06:24:34 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

I have recently become increasingly uncomfortable with my areas of ignorance with Mathematica.  The Virtual conference has some really cool demos.  In one, a website is read in and a table of data extracted.  Without patterns, it would have been very difficult.  Need a little help with an example.

Example 1 uses my old standby, the Table[] function.  Works fine.  I am attempting to get better with patterns, so I tried example 2 and 3.  They work, but gives several errors about use of stringjoin needing strings.  What am I doing wrong?

Error: StringJoin::string: String expected at position 1 in StringJoin[n].

(* Load string from WolframAlpha  *)
m WolframAlpha["usa",{{"LargestCities:CountryData",1},"ComputableData"},
PodStates->{"LargestCities:CountryData__More","LargestCities:CountryData__More"}];

(* example 1 *)
mNew=Flatten[m,1];
mNew=Drop[mNew,1];
mNew=Drop[mNew,-1];
mNew=Table[{i[[1,1]] <> i[[1,2]] <> i[[1,2]] ,i[[2]]},{i,mNew}];
Grid[mNew,Frame->All]

(* example 2 *)
Clear[n,o,p,q];
mNew=Cases[m, {{n_String,o_String,p_String},q_} -> { n <>  ", " <> o  <> ", " <>  p,q},Infinity ];
Grid[mNew,Frame->All]

(* example 3 *)
Clear[n,o,p,q];
mNew=Cases[m, {{n_,o_,p_},q_} -> { n ,  ", ", o  , ", ", p,q},Infinity ];
mNew = mNew /. {n___,q_Integer} -> {StringJoin[n],q};
Grid[mNew,Frame->All]

I even tried,
mNew = Flatten[m, 1];
mNew = Drop[mNew, 1];
mNew = Drop[mNew, -1];
mNew = Table[{Head[i[[1, 1]]], Head[i[[1, 2]]], Head[ i[[1, 2]]] ,
    i[[2]]}, {i, mNew}];
(*mNew=Table[{i[[1,1]] <> i[[1,2]] <> i[[1,2]] ,i[[2]]},{i,mNew}];*)
Grid[mNew, Frame -> All]

They are all strings!


Thanks,
Paul


Paul McHale  |  Electrical Engineer, Energetics Systems  |  Excelitas Technologies Corp.
=09
Phone:   +1 937.865.3004   |   Fax:  +1 937.865.5170   |   Mobile:   +1 937.371.2828
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Paul.McHale at Excelitas.com
www.excelitas.com



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