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# trapmf

Trapezoidal-shaped membership function

## Syntax

```y = trapmf(x,[a b c d])
```

## Description

The trapezoidal curve is a function of a vector, x, and depends on four scalar parameters a, b, c, and d, as given by

$f\left(x;a,b,c,d\right)=\left\{\begin{array}{cc}0,& x\le a\\ \frac{x-a}{b-a},& a\le x\le b\\ 1,& b\le x\le c\\ \frac{d-x}{d-c},& c\le x\le d\\ 0,& d\le x\end{array}\right\}$

or, more compactly, by

$f\left(x;a,b,c,d\right)=\mathrm{max}\left(\mathrm{min}\left(\frac{x-a}{b-a},1,\frac{d-x}{d-c}\right),o\right)$

The parameters a and d locate the "feet" of the trapezoid and the parameters b and c locate the "shoulders."

## Examples

expand all

### Trapezoid-Shaped Membership Function

```x = 0:0.1:10;
y = trapmf(x,[1 5 7 8]);
plot(x,y)
xlabel('trapmf, P=[1 5 7 8]')
ylim([-0.05 1.05])
```