How can I find it?

how can I find f(-0,3) on matlab?

Answer 1

[Walter Roberson]

There is not just one answer: it depends upon what model function you use

x = [-0.4, 0, 0.4, 0.8, 1.2]

x = 1×5

-0.4000 0 0.4000 0.8000 1.2000

fx = [-0.204, -0.07, -0.006, 0.442, 1.658]

fx = 1×5

-0.2040 -0.0700 -0.0060 0.4420 1.6580

fx03 = interp1(x, fx, -0.3)

fx03 = -0.1705

fx03s = interp1(x, fx, -0.3, 'spline')

fx03s = -0.1382

p3 = polyfit(x, fx, 3);
fx03p3 = polyval(p3, -0.3)

fx03p3 = -0.1427

The cubic fit looks pretty good.

[Furkan Ozkan]

thanks!

Answer 2

[Chunru]

You can use interp1 to interpolate. 'doc interp1' for more details.

x = [-0.4 0 0.4 0.8 1.2];
f = [-0.204 -0.07 -0.006 0.442 1.658];
y = interp1(x, f, -0.3)

y = -0.1705