Interpolating data with specifc / non-consistent "X" values:

Hey,

I've got a question that I can't seem to find within MATLAB functions. Right now, I'm trying to get an approximation for sun "yaw" data for a controller I'm trying to design. Right now, I have data at days (beginning from Jul. 15, and day 189 being Jan. 20. )

[1 95 189 277 365]

(If curious, I decided to start experiment after summer solstice happened, and there was only 1 day of sunshine I was free in the Dec. and Jan. months. So, that's why there's not an even split.)

Anyway, using an online suncalc checker, I was able to get yaw angles at each hour on these 5 days, which was nice. However, I'm running into a problem.

My plan initially was to find the polynomial fit for each hour. For instance, at 12:00 on each above day, I have yaw angles:

[56 73 84 66 56]

Now, using Excel, I get the plot in the picture.

My question is how do I generate this plot in MATLAB?

Thanks for any help in advance.

Answer 1

[Dishant Arora]

you can realize the polynomial using polyfit function:

P = polyfit(X, Y, n) % n is the order of the polynomial you want

Answer 2

[Chris]

Further comment:

I can't seem to get the picture to load. And I'm having trouble with Imgur at the moment (Firefox and Chrome), so I can't upload it.

If you do plot the data above:

X = [1 95 189 277 365] Y = [56 73 84 66 56]

with a 2nd order polynomial fit, you get (in Excel)

Y = -0,0007x^2 + 0.2569x + 56.06

R^2 = 0.8817

Answer 3

[Chris]

Thank you.