How to extend a curve until x-axis and y-axis

Hi guys! I've plotted the red curve through a set of data (.txt file of points):

How can I extend the red curve untile axes of cartesian plane ?

[Meg Noah]

Please post the .txt file. The easy answer is change the limits of the axes using xlim and ylim. But I'm guessing that's not what you want. There are several ways to extrapolate data. Generally, extrapolation is frowned on in physical sciences, but it's a very small extrapolation that you're looking for.

[Giuseppe]

the x data are (each value must be divided by 5.68):

0.1115

0.3344

0.5567

0.7782

0.9985

1.2173

1.4342

1.6488

1.8609

2.0702

2.2763

2.4788

2.6775

2.8721

3.0623

3.2478

3.4282

3.6034

3.7730

3.9367

4.0944

4.2458

4.3907

4.5288

4.6599

4.7838

4.9003

5.0093

5.1106

5.2039

5.2893

5.3665

5.4354

5.4960

5.5480

5.5915

5.6264

5.6526

5.6701

5.6789

the y data are:

0.8003

0.8256

0.8503

0.8745

0.8990

0.9228

0.9466

0.9697

0.9926

1.0152

1.0371

1.0583

1.0790

1.0992

1.1182

1.1361

1.1531

1.1681

1.1815

1.1930

1.2019

1.2078

1.2104

1.2088

1.2025

1.1907

1.1725

1.1469

1.1132

1.0701

1.0171

0.9533

0.8781

0.7914

0.6934

0.5846

0.4663

0.3400

0.2075

0.0710

As you can see, I don't have the "bounday" data points!

The curve must stop to eta=0 and to Cl=0.

[Subhadeep Koley]

Are you expecting something like below?

[Giuseppe]

No, I want to obtain this following one (i.e., I want to plot the green parts):

Answer 1

[WalterWhite]

It doesnt seem to happen with interpolation(interp1)...atleast for me. But i've come up with an alternative based on the geometry and i've explained the reason along the code. Hope this helps

[Giuseppe]

Ok, it works for the left part of figure!

Any solution for the lower part (i.e. the intersection with horizontal axis eta) ?

[WalterWhite]

It's basically the same concept for the other end. You just have to copy paste and change the values. But this is not an accurate result, mind you

[Giuseppe]

Ok, thanks!

Answer 2

[Navya Seelam]

Hi,

You can use interp1 function to interpolate your plot till x=0. There are different methods the function adopts for interpolation. You can choose from these methods to achieve appropriate interpolation. For more details on interp1 go through the link below.

https://www.mathworks.com/help/matlab/ref/interp1.html