# UI characteristic function [closed]

I have three given points:

$\qquad$A$\qquad$(0; 5.9)
$\qquad$B$\qquad$(18; 5.56)
$\qquad$C$\qquad$(22.32; 0)

I don't know how I can create a function like the one in the image below with those points. Would be great if anybody could help me!

## 2 Answers

Physically motivated answer:

points = {{0, 5.9}, {18, 5.56}, {22.32, 0}};
pointsSharp = {{0, 5.9}, {22.31, 5.89}, {22.32, 0}};
nmf = NonlinearModelFit[points,
a (1/(1 + Exp[(x - b)/c]) - 1/2), {a, b, c}, x];
nmfSharp = NonlinearModelFit[pointsSharp,
a (1/(1 + Exp[(x - b)/c]) - 1/2), {a, b, c}, x];
blue = RGBColor[17.6/100, 41.6/100, 63.1/100];
red = RGBColor[86.3/100, 13.3/100, 19.6/100];
gr = Show[
ListPlot[points, PlotStyle -> Directive[PointSize[Large], red]],
Plot[{nmfSharp[x], nmf[x]}, {x, 0, 30},
PlotStyle -> {Directive[Thick, Dashed, Black],
Directive[Thick, blue]}],
AxesLabel -> {"V", "I"},
AxesStyle -> Directive[AbsoluteThickness[1], 14, FontFamily -> "Helvetica"]
]


points = {{0, 5.9}, {18, 5.56}, {22.32, 0}};

Graphics[{Red, PointSize[Medium], Point@points,
Blue, BezierCurve[points, SplineDegree -> 1],
Thick, Green, BezierCurve[points]}, Frame -> True,
AspectRatio -> 1/GoldenRatio]