descendZero               package:xcms               R Documentation

_F_i_n_d _s_t_a_r_t _a_n_d _e_n_d _p_o_i_n_t_s _o_f _a _p_e_a_k

_D_e_s_c_r_i_p_t_i_o_n:

     Decends down the sides of a data peak and finds either the points
     greater than or equal to the zero intercept, the intercept with a
     given value, or the bottom of the first valley on each side.

_U_s_a_g_e:

     descendZero(y, istart = which.max(y))
     descendValue(y, value, istart = which.max(y))
     descendMin(y, istart = which.max(y))

_A_r_g_u_m_e_n_t_s:

       y: numeric vector with values

  istart: starting point for descent

   value: numeric value to descend to

_V_a_l_u_e:

     An integer vector of length 2 with the starting and ending
     indicies of the peak start and end points.

_A_u_t_h_o_r(_s):

     Colin A. Smith, csmith@scripps.edu

_S_e_e _A_l_s_o:

     'descendValue'

_E_x_a_m_p_l_e_s:

     normdist <- dnorm(seq(-4, 4, .1)) - .1
     descendZero(normdist)
     normdist[descendZero(normdist)]
     descendValue(normdist, .15)
     normdist[descendValue(normdist, .15)]
     descendMin(normdist)

