snake                 package:Rwave                 R Documentation

_R_i_d_g_e _E_s_t_i_m_a_t_i_o_n _b_y _S_n_a_k_e _M_e_t_h_o_d

_D_e_s_c_r_i_p_t_i_o_n:

     Estimate a ridge from a time-frequency representation, using the
     snake method.

_U_s_a_g_e:

     snake(tfrep, guessA, guessB, snakesize=length(guessB),
     tfspec=numeric(dim(modulus)[2]), subrate=1, temprate=3, muA=1,
     muB=muA, lambdaB=2 * muB, lambdaA=2 * muA, iteration=1000000,
     seed=-7, costsub=1, stagnant=20000, plot=T)

_A_r_g_u_m_e_n_t_s:

   tfrep: Time-Frequency representation (real valued). 

  guessA: Initial guess for the algorithm (frequency variable). 

  guessB: Initial guess for the algorithm (time variable). 

snakesize: the length of the initial guess of time variable. 

  tfspec: Estimate for the contribution of the noise to modulus. 

 subrate: Subsampling rate for ridge estimation. 

temprate: Initial value of temperature parameter. 

     muA: Coefficient of the ridge's derivative in cost function
          (frequency component). 

     muB: Coefficient of the ridge's derivative in cost function (time
          component). 

 lambdaB: Coefficient of the ridge's second derivative in cost function
          (time component). 

 lambdaA: Coefficient of the ridge's second derivative in cost function
          (frequency component). 

iteration: Maximal number of moves. 

    seed: Initialization of random number generator. 

 costsub: Subsampling of cost function in output. 

stagnant: maximum number of steps without move (for the stopping
          criterion) 

    plot: when set (by default), certain results will be displayed 

_D_e_t_a_i_l_s:

_V_a_l_u_e:

     Returns a structure containing: 

   ridge: 1D array (of same length as the signal) containing the ridge.

    cost: 1D array containing the cost function.

_R_e_f_e_r_e_n_c_e_s:

     See discussions in the text of ``Practical Time-Frequency
     Analysis''.

_S_e_e _A_l_s_o:

     `corona', `coronoid', `icm', `snakoid'.

