Count the total number of sequences in the FASTQ file and store in variable¶

This command uses bash commands to count the number of lines in the FASTQ file (wc-l), divides the total number of lines by 4 (there are 4 lines per read in Illumina FASTQ files). The echo command is used to print the result to the screen, which gets stored in the variable: TotalSeqs

In [1]:

TotalSeqs = !echo $((`wc -l < 2112_lane1_NoIndex_L001_R1_001.fastq` / 4))

In [2]:

#Prints the value stored in TotalSeqs.
#Notice that this is a Python string list and is not an integer!
print TotalSeqs

['16000000']

In [3]:

#Converts the value in the TotalSeqs string list at index 0 (TotalSeqs[0]) to 
#an integer value of base 10.
#This conversion will be used repeatedly throughout this notebook to allow 
#mathematical calculations using the numbers generated by bash commands.
TotalSeqs = int(TotalSeqs[0])

In [4]:

print TotalSeqs

16000000

Use bash `grep` and `wc -l` to count all the instances of the Epinext adaptor 1 sequence:¶

ACACTCTTTCCCTACACGACGCTCTTCCGATCT

In [5]:

TruSeq_adaptor1_grep = !grep -o 'ACACTCTTTCCCTACACGACGCTCTTCCGATCT ' 2112_lane1_NoIndex_L001_R1_001.fastq \
| wc -l

In [6]:

#Converts the value in the TruSeq_adaptor1_grep string list at index 0 (TruSeq_adaptor1_grep[0]) to 
#an integer value of base 10.
TruSeq_adaptor1_grep = int(TruSeq_adaptor1_grep[0])

In [7]:

print TruSeq_adaptor1_grep

Percentage of Reads Containing Epinext adaptor 1 sequence¶

In [8]:

#Calculates percentage of reads having TruSeq adaptor sequences.
#Uses "float" to convert integer values to floating point decimals. Necessary since 
#the calculation on integers would be < 1 & would result in an answer of '0'.
print ((float(TruSeq_adaptor1_grep)/TotalSeqs)*100)

0.0

Use `fastx_barcode_splitter` to identify Epinext adaptor 1 sequence.¶

The `fastx_barcode_splitter` is a component of fastx_toolkit-0.0.13.2¶

In [9]:

#The full-lengths barcode file used by fastx_barcode_splitter.
!head EpinextAdaptor1.txt

Epinext_1	ACACTCTTTCCCTACACGACGCTCTTCCGATCT

Look for Epinext adaptor 1 at beginning of lines¶

In [10]:

#Gunzip the gzipped FASTQ file.
#Pipe the output of that to fastx_barcode_splitter.pl
#fastx_barcode_splitter uses a default mismatch value = 1
#Specify barcode file (--bcfile EpinextAdaptor1.txt)
#Specify to look for barcode at beginning of file (--bol)
#Specify output location and append a prefix to new file name (--prefix ./bol_)
#Specify new file name suffix (--suffix ".fastq")
#Print data to screen and output file (tee bol_EpinextAdaptor1_stats.txt)
!gunzip -c 2112_lane1_NoIndex_L001_R1_001.fastq.gz | \
fastx_barcode_splitter.pl \
--bcfile EpinextAdaptor1.txt \
--bol \
--prefix ./bol_ \
--suffix ".fastq" | \
tee bol_EpinextAdaptor1_stats.txt

Barcode	Count	Location
Epinext_1	5	./bol_Epinext_1.fastq
unmatched	15999995	./bol_unmatched.fastq
total	16000000

In [11]:

#Uses awk to capture the second field (the "Count" column; print $2) from
#the second line (FNR == 2) of the bol_EpinextAdaptor1_stats.txt
#Stores the value in the variable EpinextAdaptor1_fastx_bol as a Python string list.
EpinextAdaptor1_fastx_bol = !awk 'FNR == 2 {print $2}' bol_EpinextAdaptor1_stats.txt

In [12]:

print EpinextAdaptor1_fastx_bol

['5']

In [13]:

#Converts the value in the TruSeqAdaptor_fastx_bol string list at index 0 (TruSeqAdaptor_fastx_bol[0]) to 
#an integer value of base 10.
EpinextAdaptor1_fastx_bol = int(EpinextAdaptor1_fastx_bol[0])

Percentage of Reads Containing Epinext adaptor 1 sequence at Beginning of Lines¶

In [14]:

#Calculates percentage of reads having Epinext adaptor 1 sequences.
#Uses "float" to convert integer values to floating point decimals. Necessary since 
#the calculation on integers would be < 1 & would result in an answer of '0'.
print ((float(EpinextAdaptor1_fastx_bol)/TotalSeqs)*100)

3.125e-05