Position-weight matrix

This module can be used to create position-weight matrices (PWM)
to describe a DNA motif. Such matrices can then be searched on
a DNA sequence, given a threshold for alignment score.

`module Biocaml_pwm: `

`sig`

type`count_matrix =`

`int array array`

Type to represent gap-free alignments. First dimension is
the sequence position, second dimension is for the alphabet.
Only DNA alphabet (A, C, G, T) is supported to rows should be
of length exactly four.

type`background = private`

`float array`

Probability distribution over an alphabet

`val flat_background : ``unit -> background`

Uniform distribution over A, C, G, T

`val background_of_sequence : ``string -> float -> background`

`background_of_sequence seq pc`

estimates the base
frequency in `seq`

using `pc`

as pseudo-counts. Typical
value for `pc`

is `0.1`

.type`t = private`

`float array array`

Representation of a PWM

`val make : ``count_matrix -> background -> t`

Builds a PWM from a count_matrix and a background

`val tandem : ``?orientation:[ `direct | `everted | `inverted ] ->`

spacer:int ->

count_matrix ->

count_matrix -> background -> t

`tandem orientation spacer cm1 cm2 bg`

builds a PWM by constructing
a composite motif: it builds `mat1`

the PWM from `cm1`

under background `bg`

(resp. `mat2`

from `cm2`

under `bg`

), then concatenates `mat1`

and `mat2`

with
`spacer`

non scoring columns in between`val reverse_complement : ``t -> t`

Reverse complement of a PWM

`val scan : ``t -> string -> float -> (int * float) list`

`scan mat seq tol`

returns the list of positions (with
corresponding scores) such that the alignment score
of `mat`

is superior to `tol`

`end`