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The goal here is to concatenate the first 6 columns from several files into a data frame in R. I am puzzled by why method (1) works but method (2) does not work. To me, both methods should be equivalent.

Answers or hints for debugging are both very welcomed.

Method (1)

ret <- sapply(fn, function(x) { (read.table(x, header = FALSE)) })
ret <- lapply(ret, function(x) {x[, 1:6]})

Method (1) correct outputs:

> head(ret)
 $`../pool.11421.poolFile`
    V1    V2     V3    V4  V5              V6
 1   1 M5132 ACAGTG 11421 351 1,2,3,4,5,6,7,8
 2   2 M6764 ACTGAT 11421 351 1,2,3,4,5,6,7,8
 3   3 M5597 AGTCAA 11421 351 1,2,3,4,5,6,7,8
 4   4 M5636 AGTTCC 11421 351 1,2,3,4,5,6,7,8
 5   5 M2463 ATCACG 11421 351 1,2,3,4,5,6,7,8
 6   6 M5792 ATGTCA 11421 351 1,2,3,4,5,6,7,8
 7   7 M6799 ATTCCT 11421 351 1,2,3,4,5,6,7,8

Method (2)

ret <- sapply(fn, function(x) { (read.table(x, header = FALSE))[, 1:6]})

Method (2) wrong outputs:

> head(ret)
        ../pool.11421.poolFile ../pool.11422.poolFile ../pool.11423.poolFile
 V1 Integer,23             Integer,48             Integer,48
 V2 Character,23           Character,48           Character,48
 V3 Character,23           Character,48           Character,48
 V4 Integer,23             Integer,48             Integer,48
 V5 Integer,23             Integer,48             Integer,48
 V6 Character,23           Character,48           Character,48
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1 回答 1

3

您的第二种方法返回一个数组。sapply有simplify论据。IfTRUE simplify2array被调用并且 R 尝试将您的数据转换为向量或数组。详情请参阅?sapply。

请尝试：

ret <- sapply(fn, function(x) { (read.table(x, header = FALSE))[, 1:6]}, simplify=FALSE)
于 2013-09-18T18:27:24.243 回答