I am doing a 2-D interpolation using interp2
. For some data values, the
interp2 command returns NaN because one of the dimensions are outside
of the range defined by the vector of known values.
Its possible to extrapolate with the interp1
command. However, Is
there a way to do this for interp2
?
Thanks
Here is the code in which I am using the interp2 command:
function [Cla] = AirfoilLiftCurveSlope(obj,AFdata,Rc,M)
% Input:
% AFdata: Airfoil coordinates.
% Rc: Local Reynolds number.
% M: Mach number for Prandtle Glauert compressibility correction.
% Output:
% Cla: 2 dimensional lift curve slopea applicable to linear region of lift polar.
load('ESDU84026a.mat');
xi = size(AFdata);
if mod(xi(1,1),2) == 0
%number is even
AFupper = flipud(AFdata(1:(xi(1,1)/2),:));
AFlower = AFdata(((xi(1,1)/2)+1):end,:);
else
%number is odd
AFupper = flipud(AFdata(1:floor((xi(1,1)/2)),:));
AFlower = AFdata((floor(xi(1,1)/2)+1):end,:);
end
t_c = Airfoil.calculateThickness(AFdata(:,2));
Y90 = ((interp1(AFupper(:,1),AFupper(:,2),0.9,'linear')) - (interp1(AFlower(:,1),AFlower(:,2),0.9,'linear')))*100;
Y99 = ((interp1(AFupper(:,1),AFupper(:,2),0.99,'linear')) - (interp1(AFlower(:,1),AFlower(:,2),0.99,'linear')))*100;
Phi_TE = (2 * atan( ( (Y90/2) - (Y99/2) )/9))*180/pi; % Degrees
Tan_Phi_Te = ( (Y90/2) - (Y99/2) )/9;
Cla_corr = interp2(Tan_Phi,Rc_cla,cla_ratio,Tan_Phi_Te,Rc,'linear');
beta =sqrt((1-M^2)); % Prandtle Glauert correction
Cla_theory = 2*pi + 4.7*t_c*(1+0.00375 * Phi_TE); % per rad
Cla = (1.05/beta) * Cla_corr * Cla_theory; % per rad
if isnan(Cla) == 1 %|| Cla > 2*pi
Cla = 2*pi;
end
end