score_trapezoid: Score a Variable With a Trapezoidal Function

In SQIpro: Comprehensive Soil Quality Index Computation and Visualization

Score a Variable With a Trapezoidal Function

Description

Applies a trapezoidal scoring function where scores are 1 within an ideal plateau [opt_low, opt_high], rise linearly from 0 at min_val to 1 at opt_low, and fall linearly from 1 at opt_high to 0 at max_val. Values outside [min_val, max_val] receive a score of 0.

This function is more flexible than score_optimum because the user explicitly controls the zero-score boundaries, making it suitable for variables with well-established critical thresholds.

Usage

score_trapezoid(x, min_val, opt_low, opt_high, max_val)

Arguments

x	Numeric vector of raw variable values.
min_val	Numeric. Value at which score becomes 0 on the low side.
opt_low	Numeric. Lower bound of the plateau (score = 1).
opt_high	Numeric. Upper bound of the plateau (score = 1).
max_val	Numeric. Value at which score becomes 0 on the high side.

Value

Numeric vector of scores in [0, 1].

References

Wymore, A.W. (1993). Model-Based Systems Engineering. CRC Press, Boca Raton, FL.

Buse, R., & Lele, S. (2003). Trapezoidal membership functions in fuzzy soil quality assessment. Geoderma, 114, 177–196.

Examples

ph <- c(3.5, 5.0, 6.5, 7.0, 7.8, 8.5, 9.5)
# pH: absolute zero below 4 and above 9; ideal 6.0-7.0
score_trapezoid(ph, min_val = 4.0, opt_low = 6.0,
                opt_high = 7.0, max_val = 9.0)

SQIpro documentation built on April 20, 2026, 5:06 p.m.