# DADA2 Truncating Reverse Read
**URL:** https://forum.qiime2.org/t/dada2-truncating-reverse-read/4667
**Category:** User Support
**Tags:** dada2, demux, summarize
**Created:** [June 21, 2018, 5:48pm UTC](https://forum.qiime2.org/t/dada2-truncating-reverse-read/4667 "2018-06-21T17:48:19Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@ninaxhua](https://forum.qiime2.org/u/ninaxhua)
#### Post date: [June 21, 2018, 5:48pm UTC](https://forum.qiime2.org/t/dada2-truncating-reverse-read/4667/1 "2018-06-21T17:48:19Z")
Hello,
I was wondering if it was concerning to see this message occur multiple times during error learning and denoising steps: "Not all sequences were the same length." This occurred when I used '0' as --p-trunc-len-r value since I didn't want to truncate the reverse read.
However, when I re-ran DADA2 with --p-trunc-len-r value set to the last sequence base position of the reverse read in the Demux visualization, I didn't encounter the message. Essentially, I did not truncate the reverse read right?
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### Author:  [@thermokarst](https://forum.qiime2.org/u/thermokarst)
#### Post date: [June 22, 2018, 12:35am UTC](https://forum.qiime2.org/t/dada2-truncating-reverse-read/4667/2 "2018-06-22T00:35:22Z")
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### Author:  [@thermokarst](https://forum.qiime2.org/u/thermokarst)
#### Post date: [June 22, 2018, 12:38am UTC](https://forum.qiime2.org/t/dada2-truncating-reverse-read/4667/3 "2018-06-22T00:38:29Z")
Hey there @ninaxhua!
> [@ninaxhua](#):
>
> I used ‘0’ as --p-trunc-len-r value since I didn’t want to truncate the reverse read.
👍
> [@ninaxhua](#):
>
> Essentially, I did not truncate the reverse read right?
No, I don't think that is right - I think you did truncate your sequences. The [`demux summarize`](https://docs.qiime2.org/2018.4/plugins/available/demux/summarize/) method only uses a subsample of reads by default (10000 reads), which means that you could actually have longer reads that just aren't represented in the viz. You could rerun and specify the `--p-n` parameter to whatever the total number of reads are to get a more complete picture.
Hope that helps! 🦖 :qiime2:
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### Author:  [@thermokarst](https://forum.qiime2.org/u/thermokarst)
#### Post date: [June 22, 2018, 12:38am UTC](https://forum.qiime2.org/t/dada2-truncating-reverse-read/4667/4 "2018-06-22T00:38:31Z")
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### Author:  [@system](https://forum.qiime2.org/u/system)
#### Post date: [July 23, 2018, 6:38am UTC](https://forum.qiime2.org/t/dada2-truncating-reverse-read/4667/5 "2018-07-23T06:38:34Z")
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