STK_SIMULATE_NOISE simulates random draws of the observation noise

 CALL: Z = stk_simulate_noise (MODEL, X)

    simulates one random draw of the observation noise in the MODEL at
    observation points X.  The input argument X can be either a numerical
    matrix or a dataframe.  The output Z has the same number of of rows as X.
    More precisely, on a factor space of dimension DIM,

     * X must have size NS x DIM,
     * Z will have size NS x 1,

    where NS is the number of simulation points.

 CALL: Z = stk_simulate_noise (MODEL, X, M)

    generates M random draws at once.  In this case, the output argument Z has
    size NS x M.

 See also: stk_generate_samplepaths