Fitting an equation to a Sine Function with NonLinearModel.fit

I am trying to fit an equation to a set of data that behaves like the sine wave. The data is graphed below:

I already tried using the "cftool" function in matlab but it did not have the equation I need.

I need to use the following equations:

y = a0 + a1*x + a2*sin(a3*x+a4)

y = a1*x + a2*sin(a3*x+a4)

y = a0 + a1*x + a2*sin(a3*x+a4) + a5*sin(a6*x+a7)

Does anyone know how to use "NonLinearModel.fit" in order to fit one of the above functions to the graphed data? The x and y matrices are listed below.

Thanks in advance!

x = [0

90

180

270

360

450

540

630

720

810

900

990

1080

1170

1260

1350

1440];

y = [0

0.00599999999997181

0.00999999999999091

0.00499999999999545

0.0029999999999859

0.0029999999999859

0.00999999999999091

0.0149999999999864

0.0159999999999627

0.0029999999999859

0.00399999999996226

0.00599999999997181

0.00199999999995271

0.0109999999999673

0.0129999999999768

0.00999999999999091

0.00399999999996226];

Answer 1

[Stephan]

"...I already tried using the "cftool" function in matlab but it did not have the equation I need...."

Did you notice that you can take adcantage of the custom function in cftool? Have a read here:

https://de.mathworks.com/help/curvefit/custom-nonlinear-models.html

[Wesley Brown]

This is great! I can’t believe I didn’t see this.

Thank you!