algorithm - Splitting strings into letter keys and integers

I have strings of the following form:

string = "ABC123DEFG456HI89UZXX1";

Letter keys of variable lengths are followed by (positive) integers.

I want to get this transformation:

{{"ABC", 123}, {"DEFG", 456}, {"HI", 89}, {"UZXX", 1}}

I have written:

chars = Characters @ string;


runs = Length /@ Split[IntegerQ @ ToExpression @ # & /@ chars]

{3, 3, 4, 3, 2, 2, 4, 1}

takes = Transpose[{# - runs + 1, #}] & [Accumulate @ runs]

{{1, 3}, {4, 6}, {7, 10}, {11, 13}, {14, 15}, {16, 17}, {18, 21}, {22, 22}}

 result =
    Partition[StringJoin /@ Map[Take[chars, #] &, takes], 2] /.
       {a_String, b_String} :> {a, ToExpression @ b}

{{"ABC", 123}, {"DEFG", 456}, {"HI", 89}, {"UZXX", 1}}

I have two questions:

(1) How could the above coding be shortened / improved? (it seems to be too long for such a trivial problem)

(2) How would a "direct" method (StringCases , StringSplit ...) look like?

Answer

You asked for shortened, improved, so here it is using RegularExpressions:

StringCases[string, RegularExpression["(\\D+)(\\d+)"] :> {"$1", ToExpression["$2"]}]

{{"ABC", 123}, {"DEFG", 456}, {"HI", 89}, {"UZXX", 1}}

Here's a version using StringSplit:

Partition[StringSplit[string, RegularExpression["(\\d+)"] :> FromDigits @ "$1"], 2]

Comments

functions - Get leading series expansion term?

Given a function f[x] , I would like to have a function leadingSeries that returns just the leading term in the series around x=0 . For example: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x)] x and leadingSeries[(1/x + 2 + (1 - 1/x^3)/4)/(4 + x)] -(1/(16 x^3)) Is there such a function in Mathematica? Or maybe one can implement it efficiently? EDIT I finally went with the following implementation, based on Carl Woll 's answer: lds[ex_,x_]:=( (ex/.x->(x+O[x]^2))/.SeriesData[U_,Z_,L_List,Mi_,Ma_,De_]:>SeriesData[U,Z,{L[[1]]},Mi,Mi+1,De]//Quiet//Normal) The advantage is, that this one also properly works with functions whose leading term is a constant: lds[Exp[x],x] 1 Answer Update 1 Updated to eliminate SeriesData and to not return additional terms Perhaps you could use: leadingSeries[expr_, x_] := Normal[expr /. x->(x+O[x]^2) /. a_List :> Take[a, 1]] Then for your examples: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x), x] leadingSeries[Exp[x], x] leadingSeries[(1/x + 2 + (1 - 1/x...

How to thread a list

I have data in format data = {{a1, a2}, {b1, b2}, {c1, c2}, {d1, d2}} Tableform: I want to thread it to : tdata = {{{a1, b1}, {a2, b2}}, {{a1, c1}, {a2, c2}}, {{a1, d1}, {a2, d2}}} Tableform: And I would like to do better then pseudofunction[n_] := Transpose[{data2[[1]], data2[[n]]}]; SetAttributes[pseudofunction, Listable]; Range[2, 4] // pseudofunction Here is my benchmark data, where data3 is normal sample of real data. data3 = Drop[ExcelWorkBook[[Column1 ;; Column4]], None, 1]; data2 = {a #, b #, c #, d #} & /@ Range[1, 10^5]; data = RandomReal[{0, 1}, {10^6, 4}]; Here is my benchmark code kptnw[list_] := Transpose[{Table[First@#, {Length@# - 1}], Rest@#}, {3, 1, 2}] &@list kptnw2[list_] := Transpose[{ConstantArray[First@#, Length@# - 1], Rest@#}, {3, 1, 2}] &@list OleksandrR[list_] := Flatten[Outer[List, List@First[list], Rest[list], 1], {{2}, {1, 4}}] paradox2[list_] := Partition[Riffle[list[[1]], #], 2] & /@ Drop[list, 1] RM[list_] := FoldList[Transpose[{First@li...

front end - keyboard shortcut to invoke Insert new matrix

I frequently need to type in some matrices, and the menu command Insert > Table/Matrix > New... allows matrices with lines drawn between columns and rows, which is very helpful. I would like to make a keyboard shortcut for it, but cannot find the relevant frontend token command (4209405) for it. Since the FullForm[] and InputForm[] of matrices with lines drawn between rows and columns is the same as those without lines, it's hard to do this via 3rd party system-wide text expanders (e.g. autohotkey or atext on mac). How does one assign a keyboard shortcut for the menu item Insert > Table/Matrix > New... , preferably using only mathematica? Thanks! Answer In the MenuSetup.tr (for linux located in the $InstallationDirectory/SystemFiles/FrontEnd/TextResources/X/ directory), I changed the line MenuItem["&New...", "CreateGridBoxDialog"] to read MenuItem["&New...", "CreateGridBoxDialog", MenuKey["m", Modifiers-...

Blog

Search This Blog