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wblplot

Weibull probability plot

Syntax

wblplot(X)
h = wblplot(X)

Description

wblplot(X) displays a Weibull probability plot of the data in X. If X is a matrix, wblplot displays a plot for each column. Use a Weibull probability plot to assess visually whether the sample data in X comes from a population with a Weibull distribution. If the sample data has a Weibull distribution, then the data appears along the reference line. Distributions other than Weibull can introduce curvature in the plot.

h = wblplot(X) returns handles to the plotted lines.

Examples

collapse all

Generate a vector r containing 50 random numbers from a Weibull distribution with parameters A = 1.2 and B = 1.5.

rng default;  % For reproducibility
r = wblrnd(1.2,1.5,50,1);

Create a Weibull probability plot to visually determine if the data comes from a Weibull distribution.

figure;
wblplot(r)

The plot indicates that the data likely comes from a Weibull distribution.

Algorithms

wblplot matches the quantiles of sample data to the quantiles of a Weibull distribution. The sample data is sorted, scaled logarithmically, and plotted on the x-axis. The y-axis represents the quantiles of the Weibull distribution, converted into probability values. Therefore, the y-axis scaling is not linear.

Where the x-axis value is the ith sorted value from a sample of size N, the y-axis value is the midpoint between evaluation points of the empirical cumulative distribution function of the data. In the case of uncensored data, the midpoint is equal to (i0.5)N. When the data includes censored observations, use probplot instead.

wblplot superimposes a reference line to assess the linearity of the plot. The line goes through the first and third quartiles of the data.

Introduced before R2006a

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