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    <p>You can <code>scan</code> and then <code>write</code> to a file(s) one line at a time.</p> <pre><code>i &lt;- 0 while({x &lt;- scan("file.csv", sep = ",", skip = i, nlines = 1, what = "character"); length(x) &gt; 1}) { write(x[1], "file1.csv", sep = ",", append = T) write(x[2], "file2.csv", sep = ",", append = T) write(x[3], "file3.csv", sep = ",", append = T) i &lt;- i + 1 } </code></pre> <p><strong>edit!! I am using the above data, copied over 1000 times. I've done a comparison of speed when we have the file connection open at all times.</strong></p> <pre><code>ver1 &lt;- function() { i &lt;- 0 while({x &lt;- scan("file.csv", sep = ",", skip = i, nlines = 1, what = "character"); length(x) &gt; 1}) { write(x[1], "file1.csv", sep = ",", append = T) write(x[2], "file2.csv", sep = ",", append = T) write(x[3], "file3.csv", sep = ",", append = T) i &lt;- i + 1 } } system.time(ver1()) # w/ close to 3K lines of data, 3 columns ## user system elapsed ## 2.809 0.417 3.629 ver2 &lt;- function() { f &lt;- file("file.csv", "r") f1 &lt;- file("file1.csv", "w") f2 &lt;- file("file2.csv", "w") f3 &lt;- file("file3.csv", "w") while({x &lt;- scan(f, sep = ",", skip = 0, nlines = 1, what = "character"); length(x) &gt; 1}) { write(x[1], file = f1, sep = ",", append = T, ncol = 1) write(x[2], file = f2, sep = ",", append = T, ncol = 1) write(x[3], file = f3, sep = ",", append = T, ncol = 1) } closeAllConnections() } system.time(ver2()) ## user system elapsed ## 0.257 0.098 0.409 </code></pre>
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    1. POHow to break a large CSV data file into individual data files using R?
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    1. COThanks. I will look into scan and write.
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    2. COThis one is ok. But I found it to be extremely slow. The Python example code opens up the files and then transverses through it. I think in this code scan opens the file goes to the read location, reads the data, then closes the file; then it repeats. Hence the slowness. Can R open a file like Python, keeps it open and traverses through it? I don't think scan is doing it.
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    3. COright, i was thinking the same thing. this link may help: http://cran.r-project.org/doc/manuals/R-data.html#Output-to-connections
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