lu.hhs

/**
 * @author Jason Reynolds
 * @param input - the matrix to be decomposed into L, U and p
 * @returns - 3 objects of type Mat - L, U and p. A lower triangular matrix, upper triangular and p
 */




//takes in raw array or Mat object and return L, U, p as decomposed objects
function lu(input) {

    *import math: ndim
    *import math: deep_copy

    if (arguments.length === 0) {
        throw new Error('Exception occurred in lu - no argument given');
    }
    else if (arguments.length > 1) {
        throw new Error('Exception occurred in lu - wrong argument number');
    }

    if (!(Array.isArray(input)) && !(input instanceof Mat) && !(input instanceof Tensor)) {
        throw new Error('Exception occurred in lu - input must be a 2-dimensional JS array, matrix or tensor');
    }

    //declare raw_in as input.clone() if Mat otherwise input
    let in_type = (input instanceof Mat) || (input instanceof Tensor);
    let raw_in = (in_type) ? input.clone() : deep_copy(input);

    //when a Mat, degrade to JS array
    if (in_type) {
        raw_in = raw_in.val;
    }

    //check: is it a vector? if so, throw error
    if (!(ndim(raw_in) === 2)) {
        throw new Error('Exception occurred in lu - not a 2d matrix');
    }
    if (raw_in.length < 2 || raw_in[0].length < 2) {
        throw new Error('Exception occurred in lu - wrong dimensions, make sure it\'s a matrix');
    }

    //mathjs lup on the raw, save as result
    let result = mathjs.lup(raw_in);
    //return the L, U and p objects as Mats
    return {
        L: mat(result.L),
        U: mat(result.U),
        p: mat(result.p)
    }
}