Eckerle4               package:NISTnls               R Documentation

_C_i_r_c_u_l_a_r _i_n_t_e_r_f_e_r_e_n_c_e _d_a_t_a

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

     The `Eckerle4' data frame has 35 rows and 2 columns giving
     transmittance as a function of wavelength.

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

       y: A numeric vector of transmittance values. 

       x: A numeric vector of wavelengths. 

_F_o_r_m_a_t:

     This data frame contains the following columns:

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

     These data are the result of a NIST study involving circular
     interference transmittance.  The response variable is
     transmittance, and the predictor variable is wavelength.

_S_o_u_r_c_e:

     Eckerle, K., NIST (197?).   Circular Interference Transmittance
     Study.

_E_x_a_m_p_l_e_s:

     data(Eckerle4)
     plot(y ~ x, data = Eckerle4)

     ## should fail - ridiculous starting value for b3
     fm1 <- nls(y ~ (b1/b2) * exp(-0.5*((x-b3)/b2)**2), data = Eckerle4, trace = TRUE,
                start = c(b1 = 1, b2 = 10, b3 = 500))

     fm2 <- nls(y ~ (b1/b2) * exp(-0.5*((x-b3)/b2)**2), data = Eckerle4, trace = TRUE,
                start = c(b1 = 1.5, b2 = 5, b3 = 450))

     ## should fail - ridiculous starting value for b3
     fm3 <- nls(y ~ (1/b2) * exp(-0.5*((x-b3)/b2)**2), data = Eckerle4, trace = TRUE,
                start = c(b2 = 10, b3 = 500), algorithm = "plinear")

     fm4 <- nls(y ~ (1/b2) * exp(-0.5*((x-b3)/b2)**2), data = Eckerle4, trace = TRUE,
                start = c(b2 = 5, b3 = 450), algorithm = "plinear")

