# Error in filtering using DADA2 **URL:** https://forum.qiime2.org/t/error-in-filtering-using-dada2/3543 **Category:** User Support **Tags:** dada2 **Created:** [March 25, 2018, 7:18am UTC](https://forum.qiime2.org/t/error-in-filtering-using-dada2/3543 "2018-03-25T07:18:36Z") **Posts on this page:** 1 **Showing post:** 11
### Author: ![thermokarst](https://forum.qiime2.org/letter_avatar_proxy/v4/letter/t/8e7dd6/32.png) [@thermokarst](https://forum.qiime2.org/u/thermokarst) #### Post date: [April 6, 2018, 12:44am UTC](https://forum.qiime2.org/t/error-in-filtering-using-dada2/3543/11 "2018-04-06T00:44:40Z")
> [@hongwei2017](#): > > I have double checked my raw sequence data, it seems like the reads number in forward and reverse is not equal. Yep, I have pointed that out now several times in this thread. > [@hongwei2017](#): > > Is there anything I can do to make the both end sequences even before going for the denoising step? There isn't anything in QIIME 2 for this, but you can try to run the following to help diagnose: ```bash qiime tools export paired-end-demux-ITS-paired-end.qza --output-dir debugging cd debugging for f in *.fastq.gz; do r=$(( $(gunzip -c $f | wc -l | tr -d '[:space:]') / 4 )); echo $r $f; done ``` Theoretically you should see output that looks similar to this: ```auto 1046 YUN3428.1_30_L001_R1_001.fastq.gz 1046 YUN3428.1_30_L001_R2_001.fastq.gz 1338 YUN3428.2_45_L001_R1_001.fastq.gz 1338 YUN3428.2_45_L001_R2_001.fastq.gz 954 YUN3428.3_13_L001_R1_001.fastq.gz 954 YUN3428.3_13_L001_R2_001.fastq.gz 897 YUN3533.1.1_37_L001_R1_001.fastq.gz 897 YUN3533.1.1_37_L001_R2_001.fastq.gz 861 YUN3533.1.2_51_L001_R1_001.fastq.gz 861 YUN3533.1.2_51_L001_R2_001.fastq.gz ``` Every two lines should correspond to a single sample (forward and reverse), the two number should be identical (these are the number of raw reads in the file) - you are looking for the pair that isn't matched. Keep us posted! 🦖 --- _[View the full topic](https://forum.qiime2.org/t/error-in-filtering-using-dada2/3543)._