meanfailtime

Mean failure times and life distribution coefficients of accelerated life model

Since R2026a

collapse all in page

Syntax

meanFailTimes = meanfailtime(mdl)
meanFailTimes = meanfailtime(mdl,stressorLevels)
[meanFailTimes,lifeCoeffs] = meanfailtime(___)

Description

meanFailTimes = meanfailtime(mdl) returns a table with variables for each stressor and a variable containing the corresponding mean failure times according to the AcceleratedLifeModel object mdl. The table contains a row for each unique stressor level in mdl.stressorLevels, and a row for the stressor level in mdl.BaselineStressorLevel (if nonempty).

To plot the mean failure times, use the meanfailplot function.

meanFailTimes = meanfailtime(mdl,stressorLevels) returns the mean failure times at the stressor levels specified by stressorLevels.

example

[meanFailTimes,lifeCoeffs] = meanfailtime(___) additionally returns a table lifeCoeffs containing the fitted life distribution coefficients at the stressor levels, using any of the input argument combinations in the previous syntaxes.

Examples

collapse all

Open Live Script

Load the diodeFailure data set, which contains simulated observations of failure times for a diode at different current levels.

load diodeFailure.mat

Fit an accelerated life model to the data in the diodeFailure table using the fitacclife function. Specify a power law life stress model and use the FailureTime table variable as the failure times.

mdl = fitacclife(diodeFailure,"FailureTime",StressModel="power")
mdl = 
AcceleratedLifeModel

Life distribution: weibull
Stress model: power

    Current    WeibullA    MeanFailureTime
    _______    ________    _______________

      10        1.4869           1.41     
       5        2.8445         2.6973     
       3         4.588         4.3506     


Log-likelihood: -3.6697

mdl is an AcceleratedLifeModel object, which contains information about the fitted model coefficient estimates. By default, the fitacclife function uses a Weibull life distribution. The first column of the displayed output lists the unique stressor levels in diodeFailure. The second and third columns list the fitted life distribution values and mean failure times, respectively.

Use the meanfailtime function to compute the predicted mean failure time and the Weibull life distribution parameter at current levels 12 and 15.

[meanFailTimes,lifeCoeffs] = meanfailtime(mdl,[12; 15])
meanFailTimes=2×2 table
    Current    MeanFailureTime
    _______    _______________

      12            1.1888    
      15           0.96474    


lifeCoeffs=2×2 table
    Current    WeibullA
    _______    ________

      12        1.2537 
      15        1.0174

Create a plot of failure time versus current level.

meanfailplot(mdl)

Figure contains an axes object. The axes object with title Failure Time Plot, xlabel Current, ylabel Failure Time contains 4 objects of type line. One or more of the lines displays its values using only markers These objects represent Mean Failure Time, 3, 5, 10.

The plot shows that the mean failure time decreases nonlinearly with increasing current level.

Input Arguments

collapse all

Accelerated life model, specified as an AcceleratedLifeModel object created using fitacclife.

Stressor levels, specified as a numeric matrix. stressorLevels must contain n columns, where n is the number of elements in mdl.StressorNames.

Data Types: single | double

Output Arguments

collapse all

Mean failure times, returned as a table. The table contains a row for each unique stressor level in mdl.stressorLevels, and a row for the stressor level in mdl.BaselineStressorLevel (if nonempty).

Fitted life distribution coefficients, returned as a table. The table contains a row for each stressor level in meanFailTimes.

Version History

Introduced in R2026a

See Also

| | | | | | | |