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alimask(1) HMMER Manual alimask(1) NAME alimask - calculate and add column mask to a multiple sequence align- ment SYNOPSIS alimask [options] msafile postmsafile DESCRIPTION alimask is used to apply a mask line to a multiple sequence alignment, based on provided alignment or model coordinates. When hmmbuild re- ceives a masked alignment as input, it produces a profile model in which the emission probabilities at masked positions are set to match the background frequency, rather than being set based on observed fre- quencies in the alignment. Position-specific insertion and deletion rates are not altered, even in masked regions. alimask autodetects in- put format, and produces masked alignments in Stockholm format. msafile may contain only one sequence alignment. A common motivation for masking a region in an alignment is that the region contains a simple tandem repeat that is observed to cause an un- acceptably high rate of false positive hits. In the simplest case, a mask range is given in coordinates relative to the input alignment, using --alirange <s>. However it is more often the case that the region to be masked has been identified in coordi- nates relative to the profile model (e.g. based on recognizing a simple repeat pattern in false hit alignments or in the HMM logo). Not all alignment columns are converted to match state positions in the profile (see the --symfrac flag for hmmbuild for discussion), so model posi- tions do not necessarily match up to alignment column positions. To remove the burden of converting model positions to alignment positions, alimask accepts the mask range input in model coordinates as well, us- ing --modelrange <s>. When using this flag, alimask determines which alignment positions would be identified by hmmbuild as match states, a process that requires that all hmmbuild flags impacting that decision be supplied to alimask. It is for this reason that many of the hmm- build flags are also used by alimask. OPTIONS -h Help; print a brief reminder of command line usage and all available options. -o <f> Direct the summary output to file <f>, rather than to stdout. OPTIONS FOR SPECIFYING MASK RANGE A single mask range is given as a dash-separated pair, like --model- range 10-20 and multiple ranges may be submitted as a comma-separated list, --modelrange 10-20,30-42. --modelrange <s> Supply the given range(s) in model coordinates. --alirange <s> Supply the given range(s) in alignment coordinates. --appendmask Add to the existing mask found with the alignment. The default is to overwrite any existing mask. --model2ali <s> Print model range(s) and the corresponding alignment range(s). No masked alignment is produced. The output is a single line for each input range, of the form i..j -> m..n with i & j representing model range values, and m & n represent- ing alignment range values. --ali2model <s> Print alignment range(s) and the corresponding model range(s). No masked alignment is produced. Because some alignment posi- tions may not map to model positions, the range(s) produced will begin with the first alignment position between <from> and <to> (inclusive) that maps to a model position, and end with the fi- nal alignment position in that range that maps to a model posi- tion. The output is a single line for each input range, of the form i..j -> m..n with i & j representing alignment range values, and m & n repre- senting model range values. If no alignment positions in the range <from>..<to> map to a model position, the output prints the input <from> and <to> mapping to nothing, with the format: i..j -> -..- (no map) . OPTIONS FOR SPECIFYING THE ALPHABET --amino Assert that sequences in msafile are protein, bypassing alphabet autodetection. --dna Assert that sequences in msafile are DNA, bypassing alphabet au- todetection. --rna Assert that sequences in msafile are RNA, bypassing alphabet au- todetection. OPTIONS CONTROLLING PROFILE CONSTRUCTION These options control how consensus columns are defined in an align- ment. --fast Define consensus columns as those that have a fraction >= sym- frac of residues as opposed to gaps. (See below for the --sym- frac option.) This is the default. --hand Define consensus columns in next profile using reference annota- tion to the multiple alignment. This allows you to define any consensus columns you like. --symfrac <x> Define the residue fraction threshold necessary to define a con- sensus column when using the --fast option. The default is 0.5. The symbol fraction in each column is calculated after taking relative sequence weighting into account, and ignoring gap char- acters corresponding to ends of sequence fragments (as opposed to internal insertions/deletions). Setting this to 0.0 means that every alignment column will be assigned as consensus, which may be useful in some cases. Setting it to 1.0 means that only columns that include 0 gaps (internal insertions/deletions) will be assigned as consensus. --fragthresh <x> We only want to count terminal gaps as deletions if the aligned sequence is known to be full-length, not if it is a fragment (for instance, because only part of it was sequenced). HMMER uses a simple rule to infer fragments: if the sequence length L is less than or equal to a fraction <x> times the alignment length in columns, then the sequence is handled as a fragment. The default is 0.5. Setting --fragthresh 0 will define no (non- empty) sequence as a fragment; you might want to do this if you know you've got a carefully curated alignment of full-length se- quences. Setting --fragthresh 1 will define all sequences as fragments; you might want to do this if you know your alignment is entirely composed of fragments, such as translated short reads in metagenomic shotgun data. OPTIONS CONTROLLING RELATIVE WEIGHTS HMMER uses an ad hoc sequence weighting algorithm to downweight closely related sequences and upweight distantly related ones. This has the ef- fect of making models less biased by uneven phylogenetic representa- tion. For example, two identical sequences would typically each receive half the weight that one sequence would. These options control which algorithm gets used. --wpb Use the Henikoff position-based sequence weighting scheme [Henikoff and Henikoff, J. Mol. Biol. 243:574, 1994]. This is the default. --wgsc Use the Gerstein/Sonnhammer/Chothia weighting algorithm [Ger- stein et al, J. Mol. Biol. 235:1067, 1994]. --wblosum Use the same clustering scheme that was used to weight data in calculating BLOSUM substitution matrices [Henikoff and Henikoff, Proc. Natl. Acad. Sci 89:10915, 1992]. Sequences are single- linkage clustered at an identity threshold (default 0.62; see --wid) and within each cluster of c sequences, each sequence gets relative weight 1/c. --wnone No relative weights. All sequences are assigned uniform weight. --wid <x> Sets the identity threshold used by single-linkage clustering when using --wblosum. Invalid with any other weighting scheme. Default is 0.62. OTHER OPTIONS --informat <s> Assert that input msafile is in alignment format <s>, bypassing format autodetection. Common choices for <s> include: stock- holm, a2m, afa, psiblast, clustal, phylip. For more informa- tion, and for codes for some less common formats, see main docu- mentation. The string <s> is case-insensitive (a2m or A2M both work). --outformat <s> Write the output postmsafile in alignment format <s>. Common choices for <s> include: stockholm, a2m, afa, psiblast, clustal, phylip. The string <s> is case-insensitive (a2m or A2M both work). Default is stockholm. --seed <n> Seed the random number generator with <n>, an integer >= 0. If <n> is nonzero, any stochastic simulations will be reproducible; the same command will give the same results. If <n> is 0, the random number generator is seeded arbitrarily, and stochastic simulations will vary from run to run of the same command. The default seed is 42. SEE ALSO See hmmer(1) for a master man page with a list of all the individual man pages for programs in the HMMER package. For complete documentation, see the user guide that came with your HM- MER distribution (Userguide.pdf); or see the HMMER web page (http://hm- mer.org/). COPYRIGHT Copyright (C) 2023 Howard Hughes Medical Institute. Freely distributed under the BSD open source license. For additional information on copyright and licensing, see the file called COPYRIGHT in your HMMER source distribution, or see the HMMER web page (http://hmmer.org/). AUTHOR http://eddylab.org HMMER 3.4 Aug 2023 alimask(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPTIONS FOR SPECIFYING MASK RANGE | OPTIONS FOR SPECIFYING THE ALPHABET | OPTIONS CONTROLLING PROFILE CONSTRUCTION | OPTIONS CONTROLLING RELATIVE WEIGHTS | OTHER OPTIONS | SEE ALSO | COPYRIGHT | AUTHOR
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