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.

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

     This data frame contains the following columns:

     _y A numeric vector of transmittance values.

     _x A numeric vector of wavelengths.


_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:

     Try <- function(expr) if (!inherits(val <- try(expr), "try-error")) val
     plot(y ~ x, data = Eckerle4)
     ## should fail - ridiculous starting value for b3
     Try(fm1 <- nls(y ~ (b1/b2) * exp(-0.5*((x-b3)/b2)**2), Eckerle4,
                    trace = TRUE,
                    start = c(b1 = 1, b2 = 10, b3 = 500)))
     Try(fm1a <- nls(y ~ (b1/b2) * exp(-0.5*((x-b3)/b2)**2), Eckerle4,
                       trace = TRUE, alg = "port",
                       start = c(b1 = 1, b2 = 10, b3 = 500)))
     Try(fm2 <- nls(y ~ (b1/b2) * exp(-0.5*((x-b3)/b2)**2),
                 Eckerle4, trace = TRUE,
                 start = c(b1 = 1.5, b2 = 5, b3 = 450)))
     Try(fm2a <- nls(y ~ (b1/b2) * exp(-0.5*((x-b3)/b2)**2),
                 Eckerle4, trace = TRUE, alg = "port",
                 start = c(b1 = 1.5, b2 = 5, b3 = 450)))
     ## should fail - ridiculous starting value for b3
     Try(fm3 <- nls(y ~ (1/b2) * exp(-0.5*((x-b3)/b2)**2),
                    Eckerle4, trace = TRUE,
                    start = c(b2 = 10, b3 = 500), algorithm = "plinear"))
     Try(fm4 <- nls(y ~ (1/b2) * exp(-0.5*((x-b3)/b2)**2), Eckerle4, trace = TRUE,
                start = c(b2 = 5, b3 = 450), algorithm = "plinear"))

