EVA_EVT 1 02 April 2001 NIST NFIS Reference Manual eva_evt finds a desired number of eigenvalues and eigenvectors. eva_evt <covfile_in><num_eva_evt_wanted><evafile><eva_desc><evtfile><evt_desc><ascii_outfiles> eva_evt finds a desired number of eigenvalues, and corresponding eigenvectors, of a covariance matrix (or really, of any symmetric positive definite real matrix). Uses CLAPACK routines, which were originally in Fortran but were converted into C using f2c. <covfile_in> The covariance matrix (really, symmetric positive definite real matrix) some of whose eigenvalues and corresponding eivenvectors are to be found. Must be a PCASYS "covariance" file. (Usually the output of meancov.) <num_eva_evt_wanted> Specifies how many eigenvalues and eigenvectors to return for the given covariance matrix. <evafile> File to be written containing the eigenvalues that are found; will be a PCASYS "matrix" file, with first dimension equal to 1 and second dimension equal to the number of eigenvalues found. The eigenvalues will be stored in decreasing order. <eva_desc> A string to be written into the eigenvalues output file as its description string. This string can be of any length, but must not contain embedded newline characters. If it contains spaces, tabs, or shell metacharacters that are not to be expanded, then it should be quoted. To leave the description empty, use '' (two single quotes, i.e. single-quoted empty string). To let eva_evt make a description (stating that this is an eigenvalues file made by eva_evt, and showing the covariance file and number of eigenvalues), use - (hyphen). <evtfile> File to be written containing the eigenvectors that are found; will be a PCASYS "matrix" file. The i'th row of this matrix will be the eigenvector corresponding to the i'th entry in the eigenvalues output file. <evt_desc> Description string for eigenvectors output file, or - to let eva_evt make the description. As per the eva_desc. <ascii_outfiles> If y, makes ascii output files; if n, binary. Binary is recommended, unless the output files must be portable across different byte orders or floating-point formats. From test/pcasys/execs/eva_evt/eva_evt.src: % eva_evt ../meancov/fv1-9.cov 128 fv1-9.eva - fv1-9.evt - n Computes the eigen-values and eigen-vectors for fv1-9.cov and sorts in decreasing order, then returns the top 128 from that list. asc2bin (1A), bin2asc (1A), lintran (1A), meancov (1A) NIST/ITL/DIV894/Image Group