Fastq quality line symbols
Hello everybody. I got a (stupid?) question: when you open a fastq file and you look at the quality line, how do you know which symbol represents a good or bad quality? I mean, is there a table somewhere with the traduction? Cause I looked on this forum, on the links that were given in some of the topics of this forum and on wikipedia, and honestly I'm lost... I also looked at an ASCII table (by searching "ASCII table" on google and well, it didn't help me at all...). I know that on wikipedia they explain how to calculate quality but I didn't arrive to do anything with that.
The thing is, I got a Fastq file and I would really like to understand what is wrong in it, cause when I do a Fastqc, the conclusion for this file is : very bad file... So I opened the fastq file and looked at the quality line, and that's when I became lost cause I can't find any table or list or document explaining which letter or symbole correpond to which quality.
For example, for the same sequence, present two times in my file, I got these quality results (fastq from Sanger/Illumina 1.9):
#1=DDFFFHHHHHJJJJJJIJJJJJJJIJJIJJHI
and
#0;@@@?@?@?@@?@)=@@=@?@@?@???@@@???
If someone can give me a link or some kind of hint, I will appreciate it. Thank you!
The thing is, I got a Fastq file and I would really like to understand what is wrong in it, cause when I do a Fastqc, the conclusion for this file is : very bad file... So I opened the fastq file and looked at the quality line, and that's when I became lost cause I can't find any table or list or document explaining which letter or symbole correpond to which quality.
For example, for the same sequence, present two times in my file, I got these quality results (fastq from Sanger/Illumina 1.9):
#1=DDFFFHHHHHJJJJJJIJJJJJJJIJJIJJHI
and
#0;@@@?@?@?@@?@)=@@=@?@@?@???@@@???
If someone can give me a link or some kind of hint, I will appreciate it. Thank you!
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