Dialectric breakdown data

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Description

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

Format

This data frame contains the following columns:

y

A numeric vector of dialectric breakdown strength values.

x1

A numeric vector of time values.

x2

A numeric vector of temperature values.

Details

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.

Source

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

Examples

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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"))