Finding value for each degree from matlab figure

After running the values I obtained from a NACA profile in Matlab along with the txt file, I perform the smoothing process. I am trying to find equivalents at every level for the figure in the appendix. How can I do it

This is the command I run for the figure I obtained:

[Alfa2D, cl2D, ~, ~]= textread('Naca LD1408 9R.txt','%f %f  %f %f');
N2D = size(Alfa2D,1);

%--------------------------------------------------------------------------    
%   Fit a Smoothing Spline Model
%--------------------------------------------------------------------------    
f = fit(Alfa2D, cl2D,'smoothingspline','SmoothingParam',0.3)

f = 
     Smoothing spline:
       f(x) = piecewise polynomial computed from p
     Coefficients:
       p = coefficient structure

figure(1); plot(f,Alfa2D,cl2D)

[Walter Roberson]

I am trying to find equivalents at every level for the figure in the appendix.

Could you explain that more?

[helin özdemir]

Hello, the Naca LD1408 9R.txt file that I used to obtain the figure is at the top of the post. The data I want to obtain is the red (fitted curve) line in the figure file. I want to obtain the values of the fitted curve line at 1 degree or 0.5 degree intervals. For example, it starts from -15 x= -15 y=0.75 x=-14 y= 0.80. Is there a command that will do this automatically and correctly?

Answer 1

[Voss]

data = readmatrix('Naca LD1408 9R.txt');
f = fit(data(:,1), data(:,2),'smoothingspline','SmoothingParam',0.3);

xi = -15:1:18; % or -15:0.5:18 or whatever
yi = f(xi);

figure
plot(f,data(:,1),data(:,2))
hold on
plot(xi,yi,'o','MarkerFaceColor','g','DisplayName','1° intervals')
set(get(gca(),'Legend'),'Location','best');