Question: Hi everyone,

I'm having trouble trying to filter blast result outputs.

So, I'm using a huge amount of sequences as queries against a certain genome in a local tblastn, which gives me an .txt output. The thing is, I need to extract the best hits, that I've defined as the lowest e-value, for each genomic region that the genome is divided.

I tried sorting in excel with the Filter command, but as the e-value is presented like '1.08e-108', the excel only considers the numbers before the 'e'. Then, in a hypothetical list containing e-values with 1.08e-108, 2.34e-10 and 1.03e-03 values, excel always choose 1.03e-03.

The next thing I tried to do was sorting each genomic region using Pandas, which I transformed the .txt output from blast in a dataframe for better manipulation, but the same thing that happened like in excel.

This way, I'm selecting manually each best hit, but it is taking too much time.

Here's an example of the output:

```
BrflORs150.1	KN907735.1	23.616	271	186	6	40	299	80310	81092	1.41e-12	75.1
BrflORs150.2	KN907735.1	24.242	264	178	6	41	296	80313	81062	7.55e-09	63.5
BrflORs155.1	KN907735.1	24.825	286	204	4	23	303	80253	81092	1.29e-17	92.4
BrflORs155.1	KN907735.1	22.388	268	188	7	33	290	181025	181798	1.24e-10	70.1
BrflORs155.1	KN907735.1	24.908	273	181	5	41	302	32141	32920	1.84e-10	69.7
BrflORs155.1	KN907735.1	24.254	268	187	7	39	298	191353	192132	2.81e-10	68.9**
BrflORs155.1	KN907685.1	24.739	287	199	8	25	303	37370	38203	9.68e-13	77.0
BrflORs155.1	KN907685.1	25.926	297	189	12	20	301	14077	14919	9.72e-09	63.9
BrflORs155.1	KN909062.1	21.379	290	204	6	23	300	50032	49199	3.01e-12	75.5
BrflORs155.1	KN909062.1	23.132	281	198	5	27	298	33061	32246	7.06e-11	70.9
BrflORs155.1	KN907432.1	25.862	290	181	8	28	300	166293	165475	2.98e-11	72.0
BrflORs155.1	KN906695.1	26.102	295	191	9	22	303	463829	464671	1.27e-10	70.1
BrflORs155.1	KN906695.1	26.689	296	188	8	22	303	485691	486533	3.83e-10	68.6
```

From those, for example, for the KN907735.1 region, I'd need to select only the query presenting e-value of 1.29e-17, because is the lowest one.

Answer: Yes! It worked perfectly, thank you guys! I'm very happy right now hahahaa, it has been consuming me for months!

Can I ask just one more question?? For each genomic region (column 2), there are more than one candidate for Best hit, because a genomic region is composed of thousands of nucleotide bases and the candidates I'm looking for have around 750bp. So, for example, in a genomic region KV926207.1, the following result is presented:

query acc.ver	subject acc.ver	% identity	alignment length	mismatches	gap opens	q. start	q. end	s. start	s. end	evalue	bit score

BrflORs155.1	KV926207.1	25.510	294	190	9	28	304	130633	131478	8.49e-14	81.6

BrflORs155.1	KV926207.1	24.014	279	191	6	32	298	142379	143188	7.75e-11	72.4

BrflORs157.1	KV926207.1	27.113	284	179	8	46	318	130675	131475	1.70e-17	92.8

BrflORs157.1	KV926207.1	26.259	278	164	7	51	310	173618	174382	1.89e-13	80.1

BrflORs157.1	KV926207.1	23.711	291	195	8	37	317	101835	102656	2.25e-13	80.1

BrflORs157.1	KV926207.1	25.000	296	182	7	34	310	142373	143197	2.31e-12	76.6

From those, the best hits may be the ones below. Because, taking for example queries BrflORs155.1 and BrflORs157.1: both hit the same genomic region that is arround 130600 to 131400, but BrflORs157.1 is chosen as the best hit because presented the lowest evalue.

The other regions comprising 101800 to 102600, 142300 to 143000 and 173000 to 174000, may contain other best hits because they are very separated from each other.

BrflORs157.1	KV926207.1	27.113	284	179	8	46	318	130675	131475	1.70e-17	92.8

BrflORs157.1	KV926207.1	25.000	296	182	7	34	310	142373	143197	2.31e-12	76.6

BrflORs157.1	KV926207.1	26.259	278	164	7	51	310	173618	174382	1.89e-13	80.1

BrflORs157.1	KV926207.1	23.711	291	195	8	37	317	101835	102656	2.25e-13	80.1

I know now how to get the lowest evalue for a certain evalue, but is there a way I can get other best hits for a certain genomic region (for example, KV926207.1), putting some kind of filter saying something like 'Take the lowest evalue in a genomic region if the subject start and end are higher than 1000bp'?

I really appreciated the help. I'm studying right now the sort command on linux so I can get a way to do that :)