| Nelson(NISTnls) | R Documentation |
The Nelson data frame has 128 rows and 3 columns of data from an
accelerated test of dialectric breakdown.
y |
A numeric vector of dialectric breakdown strength values. |
x1 |
A numeric vector of time values. |
x2 |
A numeric vector of temperature values. |
This data frame contains the following columns:
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.
Nelson, W. (1981). Analysis of Performance-Degradation Data. IEEE Transactions on Reliability. Vol. 2, R-30, No. 2, pp. 149-155.
library(NISTnls)
data(Nelson)
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)
fm1 <- nls(log(y) ~ b1 - b2*x1 * exp(-b3*x2), data = Nelson,
start = c(b1 = 2, b2 = 0.0001, b3 = -0.01), trace = TRUE,
warnOnly = TRUE)
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)
#fm3 <- nls(log(y) ~ cbind(1, -x1 * exp(-b3*x2)), data = Nelson,
# start = c(b3 = -0.01), trace = TRUE, algorithm = "plinear",
# warnOnly = TRUE)
#fm4 <- nls(log(y) ~ cbind(1, -x1 * exp(-b3*x2)), data = Nelson,
# start = c(b3 = -0.05), trace = TRUE, algorithm = "plinear",
# warnOnly = TRUE)