2019 5/20 condaインストールおよび引用追記、コメント削除
PEARはオーバーラップするペアエンドリードをマージするツール。フラグメントサイーズがリード長x2より小さい場合、ペアエンドリード間にオーバーラップが存在する。PEARはこのオーバーラップ領域を認識してマージするツールとなる。
公式ページ
https://sco.h-its.org/exelixis/web/software/pear/doc.html
インストール
cent os6でテストした。
依存
- python 2.4 (or newer)
本体 Github
#クローンするとbin/にあるビルド済みプログラムもダウンロードされる。
git clone https://github.com/stevschmid/PEAR.git
cd PEAR/bin/
chmod u+x pear-0.9.6-bin-64
#bioconda
conda install -c bioconda -y pear
> ./pear-0.9.6-bin-64
$ ./pear-0.9.6-bin-64
____ _____ _ ____
| _ \| ____| / \ | _ \
| |_) | _| / _ \ | |_) |
| __/| |___ / ___ \| _ <
|_| |_____/_/ \_\_| \_\
PEAR v0.9.6 [January 15, 2015] - [+bzlib +zlib]
Citation - PEAR: a fast and accurate Illumina Paired-End reAd mergeR
Zhang et al (2014) Bioinformatics 30(5): 614-620 | doi:10.1093/bioinformatics/btt593
License: Creative Commons Licence
Bug-reports and requests to: Tomas.Flouri@h-its.org and Jiajie.Zhang@h-its.org
Usage: pear <options>
Standard (mandatory):
-f, --forward-fastq <str> Forward paired-end FASTQ file.
-r, --reverse-fastq <str> Reverse paired-end FASTQ file.
-o, --output <str> Output filename.
Optional:
-p, --p-value <float> Specify a p-value for the statistical test. If the computed
p-value of a possible assembly exceeds the specified p-value
then paired-end read will not be assembled. Valid options
are: 0.0001, 0.001, 0.01, 0.05 and 1.0. Setting 1.0 disables
the test. (default: 0.01)
-v, --min-overlap <int> Specify the minimum overlap size. The minimum overlap may be
set to 1 when the statistical test is used. However, further
restricting the minimum overlap size to a proper value may
reduce false-positive assembles. (default: 10)
-m, --max-assembly-length <int> Specify the maximum possible length of the assembled
sequences. Setting this value to 0 disables the restriction
and assembled sequences may be arbitrary long. (default: 0)
-n, --min-assembly-length <int> Specify the minimum possible length of the assembled
sequences. Setting this value to 0 disables the restriction
and assembled sequences may be arbitrary short. (default:
50)
-t, --min-trim-length <int> Specify the minimum length of reads after trimming the low
quality part (see option -q). (default: 1)
-q, --quality-threshold <int> Specify the quality score threshold for trimming the low
quality part of a read. If the quality scores of two
consecutive bases are strictly less than the specified
threshold, the rest of the read will be trimmed. (default:
0)
-u, --max-uncalled-base <float> Specify the maximal proportion of uncalled bases in a read.
Setting this value to 0 will cause PEAR to discard all reads
containing uncalled bases. The other extreme setting is 1
which causes PEAR to process all reads independent on the
number of uncalled bases. (default: 1)
-g, --test-method <int> Specify the type of statistical test. Two options are
available. (default: 1)
1: Given the minimum allowed overlap, test using the highest
OES. Note that due to its discrete nature, this test usually
yields a lower p-value for the assembled read than the cut-
off (specified by -p). For example, setting the cut-off to
0.05 using this test, the assembled reads might have an
actual p-value of 0.02.
2. Use the acceptance probability (m.a.p). This test methods
computes the same probability as test method 1. However, it
assumes that the minimal overlap is the observed overlap
with the highest OES, instead of the one specified by -v.
Therefore, this is not a valid statistical test and the
'p-value' is in fact the maximal probability for accepting
the assembly. Nevertheless, we observed in practice that for
the case the actual overlap sizes are relatively small, test
2 can correctly assemble more reads with only slightly
higher false-positive rate.
-e, --empirical-freqs Disable empirical base frequencies. (default: use empirical
base frequencies)
-s, --score-method <int> Specify the scoring method. (default: 2)
1. OES with +1 for match and -1 for mismatch.
2: Assembly score (AS). Use +1 for match and -1 for mismatch
multiplied by base quality scores.
3: Ignore quality scores and use +1 for a match and -1 for a
mismatch.
-b, --phred-base <int> Base PHRED quality score. (default: 33)
-y, --memory <str> Specify the amount of memory to be used. The number may be
followed by one of the letters K, M, or G denoting
Kilobytes, Megabytes and Gigabytes, respectively. Bytes are
assumed in case no letter is specified.
-c, --cap <int> Specify the upper bound for the resulting quality score. If
set to zero, capping is disabled. (default: 40)
-j, --threads <int> Number of threads to use
-z, --nbase When merging a base-pair that consists of two non-equal
bases out of which none is degenerate, set the merged base
to N and use the highest quality score of the two bases
-h, --help This help screen.
0.9.6の64bit版実行ファイルを"pear"とリネームして/usr/local/bin/に移動した。
ラン
ペアエンドリードのマージ。
pear -f pair1.fq -r pair2.fq -o merged
> ls -al |head -n 5
-rw-r--r-- 1 uesaka user 159M May 23 17:18 merge.assembled.fastq
-rw-r--r-- 1 uesaka user 26M May 23 17:18 merge.unassembled.forward.fastq
-rw-r--r-- 1 uesaka user 20M May 23 17:18 merge.unassembled.reverse.fastq
drwxr-xr-x 350 uesaka uesaka 36K May 23 17:15 .
-rw-r--r-- 1 uesaka user 0 May 23 17:15 merge.discarded.fastq
ランが終わると、マージされたfastqとされなかったfastqが別々に出力される。
引用
PEAR: a fast and accurate Illumina Paired-End reAd mergeR
Bioinformatics. 2014 Mar 1;30(5):614-20
Zhang J, Kobert K, Flouri T, Stamatakis A
関連
