## RSAT - Help about patser

Copyright 1990, 1994, 1995, 1996, 2000, 2001 Gerald Z. Hertz May be copied for noncommercial purposes. Author: Gerald Z. Hertz hertz@colorado.edu PATSER (version 3d) This program scores the L-mers (subsequences of length L) of the indicated sequences against the indicated alignment or weight matrix. The elements of an alignment matrix are simply the number of times that the indicated letter is observed at the indicated position of a sequence alignment. Such elements must be processed before the matrix can be used to score an L-mer (e.g., Hertz and Stormo, 1999, Bioinformatics, 15:563-577). A weight matrix is a matrix whose elements are in a form considered appropriate for scoring an L-mer. Each element of an alignment matrix is converted to an element of a weight matrix by first adding pseudo-counts in proportion to the a priori probability of the corresponding letter (see option "-b" in section 1 below) and dividing by the total number of sequences plus the total number of pseudo-counts. The resulting frequency is normalized by the a priori probability for the corresponding letter. The final quotient is converted to an element of a weight matrix by taking its natural logarithm. The use of pseudo-counts here differs from previous versions of this program by being proportional to the a priori probability. Version 3 of this program differs from previous versions by also numerically estimating the p-value of the scores. The p-value calculated here is the probability of observing a particular score or higher at a particular sequence position and does NOT account for the total amount of sequence being scored. P-values are estimated by the method described in Staden, 1989, CABIOS, p. 89--96. The relative value for each element of the weight matrix is approximated by integers in a range determined by the "-R" and "-M" options (section 6 below). The p-value is calculated for each possible integer score and the values are stored. The actual scores for the sequences are determined from the true weight matrix. The true scores are converted to their corresponding integer values and their p-values are looked up. Matrices can be either horizontal or vertical. In a horizontal matrix, the columns correspond to the positions within the pattern, and the rows correspond to the letters. Each row begins with the corresponding letter (or integer, if the "-i" option is used). In a vertical matrix, the rows correspond to the positions within the pattern, and the columns correspond to the letters. The first row contains the letters (or integers, if the "-i" option is used) corresponding to each column. In both types of matrices, spaces, tabs, and vertical bars (|) are ignored. The output of the "consensus" and "wconsensus" programs consists of horizontal alignment matrices. The input files can contain comments according to the following convention. The portion of a line following a ';', '%', or '#' is considered a comment and is ignored. Comments can begin anywhere in a line and always end at the end of the line. The output of this program is sent to the standard output. The following options can be determined on the command line. 0) -h: print these directions. 1) Matrix options. -m filename: (default name is "matrix") file containing the matrix. -w: the matrix is a weight matrix (default: alignment matrix) -b number: a non-negative number indicating the total number of pseudo-counts added to each alignment position (default: 1). Before converting an alignment matrix to a weight matrix, the total pseudo-counts multiplied by the a priori probability (see section 3 below) of the corresponding letter is added to each matrix element. -v: the matrix is a vertical matrix (default: horizontal matrix). -p: print the weight matrix derived from the alignment matrix. 2) -f filename: this file (default: read from the standard input) contains the names of the sequences. The corresponding sequence may follow its name if the sequence is enclosed between backslashes (\). Otherwise, the sequence is assumed to be in a separate file having the indicated name. In the sequences, whitespace, slashes (/), periods, dashes (unless part of an integer when the "-i" option is used), and comments beginning with ';', '%', or '#' are ignored. When using letter characters (i.e., with the "-a" or "-A" alphabet option), integers are also ignored so that the sequence file can contain positional information. When using integer characters (i.e., with the "-i" alphabet option) the integers must be separated by whitespace. A "-c" preceding the name of a sequence file indicates that the corresponding sequence is circular. 3) Alphabet options---the three options in this section are mutually exclusive (default: "-a alphabet"). The a priori probabilities mentioned below are used when converting an alignment matrix to a weight matrix. -a filename: file containing the alphabet and normalization information. Each line contains a letter (a symbol in the alphabet) followed by an optional normalization number (default: 1.0). The normalization is based on the relative a priori probabilities of the letters. For nucleic acids, this might be be the genomic frequency of the bases or the frequencies observed in the data used to generate the alignment. In nucleic acid alphabets, a letter and its complement appear on the same line, separated by a colon (a letter can be its own complement, e.g. when using a dimer alphabet). Complementary letters may use the same normalization number. Only the standard 26 letters are permissible; however, when the "-CS" option is used, the alphabet is case sensitive so that a total of 52 different characters are possible. POSSIBLE LINE FORMATS WITHOUT COMPLEMENTARY LETTERS: letter letter normalization POSSIBLE LINE FORMATS WITH COMPLEMENTARY LETTERS: letter:complement letter:complement normalization letter:complement normalization:complement's_normalization -i filename: same as the "-a" option, except that the symbols of the alphabet are represented by integers rather than by letters. Any integer permitted by the machine is a permissible symbol. -A alphabet_and_normalization_information: same as "-a" option, except information appears on the command line (e.g., -A a:t 3 c:g 2). 4) Alphabet modifiers indicating whether ascii alphabets are case sensitive---the two options in this section are mutually exclusive with each other and with the "-i" option (default: ascii alphabets are case insensitive). -CS: ascii alphabets are case sensitive. -CM: ascii alphabets are case insensitive, but mark the location of lowercase letters by printing a line containing their locations. This option is useful when lowercase letters indicate a functional landmark such as a transcriptional start in a DNA sequence. 5) Options for adjusting or restricting which scores are printed. The "-ls", "-li", and "-lp" options are mutually exclusive. -c: also score the complementary sequences. The complements are determined by the program and are not explicitly stated in the sequence files. -ls number: lower threshold for printing scores, inclusive (formerly the -l option). -li: assume that the maximum ln(p-value) for printing scores equals the negative of the sample-size adjusted information content; indirectly determines the lower threshold for printing scores. -lp number: the maximum ln(p-value) for printing scores; indirectly determines the lower threshold for printing scores. -u number: upper threshold for printing scores, exclusive. -t: just print the top score for each sequence. -t number: print the indicated number of top scores for each sequence. -ds: if the "-t number" option is used, print the top scores for each sequence in the order of decreasing score (default: order the scores according to their position within the sequence). -e number: the small difference for considering 2 scores equal (default: 0.000001) 6) Options indicating how unrecognized symbols are treated (default: -d1). Symbols are letters when option "-a" or "-A" is used; symbols are integers when option "-i" is used. The following three options are mutually exclusive. -d0: treat unrecognized symbols as errors and exit the program. -d1: treat unrecognized symbols as discontinuities, but print a warning. Treating a symbol as a discontinuity means that any L-mer containing the unrecognized symbol will be ignored. -d2: treat unrecognized symbols as discontinuities, and print NO warning. 7) Options for adjusting the estimation of p-value. If the -R option is set to zero, the p-value is not estimated. -R number: the range for approximating a column of the weight matrix with integers (default: 10000). This number is the difference between the largest and smallest integers used to estimate the scores. Higher values increase precision, but will take longer to calculate the table of p-values. -M number: the minimum score for approximating p-values (default: 0). Higher values will increase precision, but may miss interesting scores.