icdf

Inverse cumulative distribution function of accelerated life model

Since R2026a

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Syntax

finv = icdf(mdl,p)
finv = icdf(mdl,p,stressorLevel)

Description

finv = icdf(mdl,p) returns the inverse cumulative distribution function (icdf) of the AcceleratedLifeModel object mdl at the stressor level in mdl.BaselineStressorLevel, evaluated at the probability values in p. If mdl.BaselineStressorLevel is empty, icdf uses the smallest stressor level (or smallest combination of stressor levels) in mdl.StressorLevels.

example

finv = icdf(mdl,p,stressorLevel) computes the icdf at the stressor level specified by stressorLevel.

example

Examples

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Open Live Script

Load the partFailure data set, which contains simulated observations of failure times for an assembly line part at specific humidity and temperature levels.

load partFailure.mat

Fit an accelerated life model to the data in the partFailure table using the fitacclife function. Use the FailureTime table variable as the failure times, and the other table variables as the stressors.

mdl = fitacclife(partFailure,"FailureTime");

Calculate the inverse cumulative distribution function (icdf) at 90% humidity and 35 degrees, and 90% humidity and 20 degrees. Evaluate the icdf at 10 equally spaced probability values between 0.1 and 0.9.

pts = linspace(0.05,0.9,10);
icdfval = [icdf(mdl,pts); icdf(mdl,pts,[90,20])]
icdfval = 2×10

    4.9953    5.4502    5.6944    5.8737    6.0227    6.1562    6.2834    6.4119    6.5525    6.7298
    1.3842    1.5102    1.5779    1.6275    1.6688    1.7058    1.7411    1.7767    1.8156    1.8648

Create a plot of the icdf values for the two stressor levels.

plot(pts,icdfval,"-o")
xlabel("Probability")
ylabel("ICDF Value")
legend(["Humidity = 90, Temperature = 35", ...
    "Humidity = 90, Temperature = 20"],Location="east")

Figure contains an axes object. The axes object with xlabel Probability, ylabel ICDF Value contains 2 objects of type line. These objects represent Humidity = 90, Temperature = 35, Humidity = 90, Temperature = 20.

The icdf values are consistently lower at the lower temperature stressor level.

Input Arguments

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

Probability values at which to evaluate the icdf, specified as a vector of nonnegative scalar values.

Data Types: single | double

Stressor level, specified as a numeric vector of the same length as mdl.StressorNames.

Data Types: single | double

Output Arguments

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Inverse cumulative distribution function values, returned as a numeric vector with the same dimensions as p.

Version History

Introduced in R2026a

See Also

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