What does the "N" column mean of the TBLASTX output?

Question

[2351688559]

Dear all,

When I use TBLASTX, I found the result gives an additional column "N", which never appears if using other programs. I really don't know what it means....I even wounder, if this really meaningful? Would any one tell me what it is? Thank you!!

[Sej Modha]

Is it possible for you to provide a sample output with this column "N" ?

[2351688559]

! it is like this:

[st.ph.n]

Can you provide your blast cmd? Or did you run on the web?

Answer 1

[Pierre Lindenbaum]

defined in https://github.com/LeeBergstrand/NCBI_Tools/blob/281d543937237a80364105b4d14b3671136e06aa/src/objtools/align_format/showdefline.cpp#L85

used here: https://github.com/LeeBergstrand/NCBI_Tools/blob/281d543937237a80364105b4d14b3671136e06aa/src/objtools/align_format/showdefline.cpp#L663 when eShowSumN is set

eShowSumN is defined in https://github.com/LeeBergstrand/NCBI_Tools/blob/281d543937237a80364105b4d14b3671136e06aa/include/objtools/align_format/showdefline.hpp#L91

 eShowSumN = (1 << 4), //Sum_n in blast score structure

sum_n is https://github.com/LeeBergstrand/NCBI_Tools/blob/281d543937237a80364105b4d14b3671136e06aa/include/objtools/align_format/showdefline.hpp#L347

so what is this sum_n ? I wonder if it's not the number of hsp (?)

Answer 2

[astokar]

The number in the "N" column indicates how many HSPs were used in computing the statistics for the sequence. If the number is greater than 1, the scores of multiple HSPs were combined to produce the result.