I have twenty data files each contains 1000 lines ("a1.txt, a2.txt....a20.txt"). Now I want to add all these files to a single file and keep the line sequence as followed by the input files (first 1000 from a1.txt, next 1000 from a2.txt and so on). How can I do that?
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$\begingroup$ Hi Xavier and welcome! To make the most of Mma.SE start by taking the tour now. It will help us to help you if you write an excellent question. Edit if improvable, show due diligence, give brief context, include minimal working example of code and data in formatted form. As you receive give back, vote and answer questions, keep the site useful, be kind, correct mistakes and share what you have learned. $\endgroup$– rhermansJun 23, 2018 at 14:27
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$\begingroup$ There are things to do after your question is answered. It's a good idea to stay vigilant for some time, better approaches may come later improving over previous replies. Experienced users may point alternatives, caveats or limitations. New users should test answers before voting and wait 24 hours before accepting the best one. Participation is essential for the site, please do your part. $\endgroup$– rhermansJun 23, 2018 at 14:31
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$\begingroup$ Oh Yes. I am learning Mathematica for data analysis (in Windows) $\endgroup$– XavierJun 23, 2018 at 14:32
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$\begingroup$ I pointed out an issue to the answer you accepted. Can you comment if that's a problem or not? $\endgroup$– rhermansJun 24, 2018 at 8:47
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2 Answers
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A: Do you need to do this in Mathematica? You can just use the shell command
catin Unix / Mac OS. (This question is the reverse of the question "Splitting a text file into smaller text files by line numbers using Mathematica", which I answered yesterday.)X: I am learning Mathematica for data analysis (in Windows)
Direct commands
Unix paths are used below -- it is better to construct the file names with FileNameJoin for OS-independent behavior.
fnames = FileNames["~/Downloads/a*.txt"];
texts = Import /@ fnames;
Export["~/Downloads/allInOne.txt", StringRiffle[texts, "\n"], "Text"]
Unix / Mac OS
Mentioning this for completeness...
In Unix / Mac OS we can use the command cat. From within Mathematica we can make this call:
Run["cat ~/Downloads/a*.txt > ~/Downloads/allInOne.txt"]
answered Jun 23, 2018 at 14:39
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$\begingroup$ +1 For cat - I did the very same thing just a few days ago. Much simpler than using mathematica $\endgroup$ Jun 23, 2018 at 17:54
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$\begingroup$ @PerAlexandersson Yeah, often enough a Unix commands one-liner is a good alternative to data analysis analysis scripts with other languages/systems. Here is an example, "Command-line Tools can be 235x Faster than your Hadoop Cluster". $\endgroup$ Jun 23, 2018 at 18:45
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$\begingroup$ Your solution has the problem that it'a not keeping the order of the files, contrary to the OP's request to " keep the line sequence as followed by the input files". You
fnamesgives{"a10.txt", "a11.txt", "a12.txt", "a13.txt", "a14.txt", "a15.txt","a16.txt", "a17.txt", "a18.txt", "a19.txt", "a1.txt", "a20.txt", "a2.txt", "a3.txt", "a4.txt", "a5.txt", "a6.txt", "a7.txt", "a8.txt", "a9.txt"}. Presumably thecat` solution suffers from the same? $\endgroup$– rhermansJun 24, 2018 at 8:43
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OpenRead OpenWrite ReadStringWriteString
Module[
{
newfilename = "all.txt",
wfile, rfile, str
},
wfile = OpenWrite[newfilename];
Table[
rfile = OpenRead[StringTemplate["File``.txt"][k]];
str = ReadString[rfile];
Close[rfile];
WriteString[wfile, str];
, {k, 1, 20}
];
Close[newfilename]
]
Import and Export
Export[
"All2.txt",
StringJoin@Table[
Import[StringTemplate["File``.txt"][k], "String"]
, {k, 1, 20}
]
, "String"
]
To test my answers I created some files like this
SystemOpen@SetDirectory[$TemporaryDirectory]
Array[
Export[StringTemplate["File``.txt"][#], (# 1000 + Range[1000]),
"CSV"] &
, 20
];
Range[1001, 21000] == Flatten@Import["All.txt", "Table"]
(* True *)
Range[1001, 21000] == Flatten@Import["All2.txt", "Table"]
(* True *)
