probplot

Plot failure probabilities of accelerated life model

Since R2026a

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Syntax

probplot(mdl)
probplot(ax,mdl)
h = probplot(___)

Description

probplot(mdl) creates a scatter plot of failure probability versus failure time for the stressor levels mdl.StressorLevels in the AcceleratedLifeModel object mdl. The probplot function plots each row in mdl.StressorLevels using marker symbols, and draws a reference line for each unique stressor level. The reference line connects the first and third quartiles of the failure time data for that stressor level and extends to the ends of the data.

For you to create a probability plot, mdl.StressorLevels must have more than one row for each unique stressor level.

example

probplot(ax,mdl) uses the plot axes specified by the Axes object ax.

h = probplot(___) returns the handles (h) to the reference lines in the probability plot, using any of the input argument combinations in the previous syntaxes.

Examples

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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. Use the FailureTime table variable as the failure times.

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

Life distribution: weibull
Stress model: arrhenius

    Current    WeibullA    MeanFailureTime
    _______    ________    _______________

      10        1.5323         1.4721     
       5        2.4956         2.3975     
       3        4.7821         4.5941     


Log-likelihood: 0.4676

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

Create a probability plot.

probplot(mdl)

Figure contains an axes object. The axes object with title Probability Plot for Weibull Distribution, xlabel Failure Time, ylabel Failure Probability contains 6 objects of type functionline, line. One or more of the lines displays its values using only markers These objects represent 10, 5, 3.

The log-log scatter plot of failure probability versus failure time shows each observation in the data, grouped by stressor level. The dashed lines are linear regression fits to the failure times belonging to each group.

The plot indicates that failure times are shorter at higher current levels, and that the failure probability increases nonlinearly with time at each stressor level.

Input Arguments

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

Axes for the plot, specified as an Axes object. If you do not specify ax, then probplot creates the plot using the current axes. For more information on creating an Axes object, see axes.

Version History

Introduced in R2026a

See Also

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