# Filtered and denoised reads

**URL:** https://forum.qiime2.org/t/filtered-and-denoised-reads/9471
**Category:** User Support
**Created:** [May 1, 2019, 1:22pm UTC](https://forum.qiime2.org/t/filtered-and-denoised-reads/9471 "2019-05-01T13:22:24Z")
**Posts on this page:** 5
**Page:** 1

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### Author: ![Yogesh\_Gupta](https://forum.qiime2.org/user_avatar/forum.qiime2.org/yogesh_gupta/32/9097_2.png) [@Yogesh\_Gupta](https://forum.qiime2.org/u/Yogesh_Gupta)
#### Post date: [May 1, 2019, 1:22pm UTC](https://forum.qiime2.org/t/filtered-and-denoised-reads/9471/1 "2019-05-01T13:22:25Z")

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From dada2 result table, it looks like filtered and denoised read is the

 ![IMG_20190501_140629](https://forum-qiime2-org.s3.dualstack.us-west-2.amazonaws.com/original/2X/b/b414f7bb3ed469b489f3b163b7f840f693a283a2.jpeg) same.

Please correct me if I am wrong?

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### Author: ![thermokarst](https://forum.qiime2.org/letter_avatar_proxy/v4/letter/t/8e7dd6/32.png) [@thermokarst](https://forum.qiime2.org/u/thermokarst)
#### Post date: [May 2, 2019, 2:10pm UTC](https://forum.qiime2.org/t/filtered-and-denoised-reads/9471/2 "2019-05-02T14:10:18Z")

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> [@Yogesh\_Gupta](#):
>
> it looks like filtered and denoised read is the same.

Yep! That means that all of the reads that passed the filtering step also passed the denoising step. You lost 0% of your reads on denoising.

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### Author: ![Yogesh\_Gupta](https://forum.qiime2.org/user_avatar/forum.qiime2.org/yogesh_gupta/32/9097_2.png) [@Yogesh\_Gupta](https://forum.qiime2.org/u/Yogesh_Gupta)
#### Post date: [May 2, 2019, 3:52pm UTC](https://forum.qiime2.org/t/filtered-and-denoised-reads/9471/3 "2019-05-02T15:52:20Z")

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Hi @thermokarst,

Thanks, I am actually not able able to understand what exactly it does at the filtering step and then at denoising step?

How the filtering is separated from denoising?

Regards  
Yogesh

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### Author: ![yakshi.ortiz](https://forum.qiime2.org/user_avatar/forum.qiime2.org/yakshi.ortiz/32/4170_2.png) [@yakshi.ortiz](https://forum.qiime2.org/u/yakshi.ortiz)
#### Post date: [May 2, 2019, 8:30pm UTC](https://forum.qiime2.org/t/filtered-and-denoised-reads/9471/4 "2019-05-02T20:30:23Z")

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Hi Yogesh,

If I understand right, what the **denoising step** does is to correct sequencing errors at nucleotide level. This is why you will see very low to no loss at this step. The **filtering step** removes sequences based on the selected _max-ee_ value. The max-ee is the sum of probabilities that each of your nucleotides were called incorrectly (this is based on the phred score of each of your nucleotides in a given sequences). If that sum is more than the selected max-ee, then your sequence is discarded. You can read more at this [link](https://www.drive5.com/usearch/manual/exp_errs.html).

I hope that helps you a bit!  
Yakshi

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### Author: ![system](https://forum-qiime2-org.s3.dualstack.us-west-2.amazonaws.com/original/3X/2/1/21af5fe23cb6f4579467c66a9ed94e55274ca7bd.svg) [@system](https://forum.qiime2.org/u/system)
#### Post date: [June 3, 2019, 2:35am UTC](https://forum.qiime2.org/t/filtered-and-denoised-reads/9471/5 "2019-06-03T02:35:40Z")

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