Nelson                package:NISTnls                R Documentation

_D_i_a_l_e_c_t_r_i_c _b_r_e_a_k_d_o_w_n _d_a_t_a

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

     The 'Nelson' data frame has 128 rows and 3 columns of data from an
     accelerated test of dialectric breakdown.

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

     This data frame contains the following columns:

     _y A numeric vector of dialectric breakdown strength values.

     _x_1 A numeric vector of time values.

     _x_2 A numeric vector of temperature values.


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

     These data are the result of a study involving the analysis of
     performance degradation data from accelerated tests, published in
     IEEE Transactions on Reliability.  The response variable is
     dialectric breakdown strength in kilo-volts, and the predictor
     variables are time in weeks and temperature in degrees Celsius.

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

     Nelson, W. (1981).   Analysis of Performance-Degradation Data.  
     IEEE Transactions on Reliability. Vol. 2, R-30, No. 2, pp.
     149-155.

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

     Try <- function(expr) if (!inherits(val <- try(expr), "try-error")) val
     plot(y ~ x1, data = Nelson, log = "y")
     plot(y ~ x2, data = Nelson, log = "y")
     coplot(y ~ x1 | x2, data = Nelson)
     coplot(y ~ x2 | x1, data = Nelson)

     Try(fm1 <- nls(log(y) ~ b1 - b2*x1 * exp(-b3*x2), data = Nelson,
                start = c(b1 = 2, b2 = 0.0001, b3 = -0.01), trace = TRUE))
     Try(fm1a <- nls(log(y) ~ b1 - b2*x1 * exp(-b3*x2), data = Nelson,
                 trace = TRUE, alg = "port",
                 start = c(b1 = 2, b2 = 0.0001, b3 = -0.01)))

     Try(fm2 <- nls(log(y) ~ b1 - b2*x1 * exp(-b3*x2), data = Nelson,
                start = c(b1 = 2.5, b2 = 0.000000005, b3 = -0.05), trace = TRUE))
     Try(fm2 <- nls(log(y) ~ b1 - b2*x1 * exp(-b3*x2), data = Nelson,
                trace = TRUE, alg = "port", 
                start = c(b1 = 2.5, b2 = 0.000000005, b3 = -0.05)))

     Try(fm3 <- nls(log(y) ~ cbind(1, -x1 * exp(-b3*x2)), data = Nelson,
                start = c(b3 = -0.01), trace = TRUE, algorithm = "plinear"))

     Try(fm4 <- nls(log(y) ~ cbind(1, -x1 * exp(-b3*x2)), data = Nelson,
                start = c(b3 = -0.05), trace = TRUE, algorithm = "plinear"))

