export - Splitting a text file into smaller text files by line numbers using Mathematica

Is it possible to split a large text file into smaller files by line numbers in Mathematica?

Answer

Yes, of course.

text = Import["http://www.norvig.com/big.txt"];

StringLength[text]

(* 6488665 *)

lines = StringSplit[text, "\n"];
Length[lines]

(* 128457 *)

breaks = Union[Append[Range[1, Length[lines], 20000], Length[lines]]];


MapIndexed[
 Export["~/Downloads/textPart" <> ToString[#2[[1]]] <> ".txt", 
  Take[lines, #1], "Text"] &, Partition[breaks, 2, 1]]

(* {"~/Downloads/textPart1.txt", "~/Downloads/textPart2.txt", \
"~/Downloads/textPart3.txt", "~/Downloads/textPart4.txt", \
"~/Downloads/textPart5.txt", "~/Downloads/textPart6.txt", \
"~/Downloads/textPart7.txt"}*)

Verification with Unix / Mac OS commands:

[14:40:26]Downloads> ls | grep textPart | xargs -Iaaa wc aaa
   20000  239243 1398793 textPart1.txt
   20000  166040 1042501 textPart2.txt
   20000  155655  948331 textPart3.txt
   20000  166764  948771 textPart4.txt
   20000  169422  964634 textPart5.txt
   20000  167882  957716 textPart6.txt
    8456   30737  228187 textPart7.txt

Comments

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equation solving - Invert and fit implicitly defined curve

I need to fit an implicitly defined curve. I thought I could get some data out of Solve , and then using FindFit . Therefore, I would like to find the relation the parametric curve defined by $F(x,y)=0$: Solve[-(1/2) + 1/2 (0.41202 BesselK[0, 0.1 Sqrt[x^2 + y^2]] + (0.101483 x BesselK[1, 0.1 Sqrt[x^2 + y^2]])/Sqrt[x^2 + y^2]) == 0, y] But I can't get an output: Solve was unable to solve the system with inexact coefficients or the system obtained by direct rationalization of inexact numbers present in the system. Since many of the methods used by Solve require exact input, providing Solve with an exact version of the system may help. >> Edit: In particular, I would like to fit the data coming from the curve with the expression of another curve, and not with a function $f(x)$. In particular, since this clearly looks like a cardioid , I would like it to fit to something like it. What other strategies could I try?

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