Interpolating Airfoil Data

Hi everyone, I downloaded a library with all different kinds of airfoils from NACA to EPPLER etc... I'm running a potential flow code and essentially I want to be able to control the number of panels on the airfoil(user specified) for accuracy purposes. The Library however has airfoil set at 35 coordinate points. I've been trying to use the interpolate function but no cigar my numbers are off. Can anyone look at this function and see if there's any other way to make it more efficient or spot the errors I'm going through? For a general purpose it does the job there's only a couple of points that are offset but I guess I'm looking for a sleeker interpolation. I just noticed that my code isn't commented sorry about that...

airfoil_data = [
1.0000     0.00063
0.9500     0.00403
0.9000     0.00724
0.8000     0.01312
0.7000     0.01832
0.6000     0.02282
0.5000     0.02647
0.4000     0.02902
0.3000     0.03001
0.2500     0.02971
0.2000     0.02869
0.1500     0.02673
0.1000     0.02341
0.0750     0.02100
0.0500     0.01777
0.0250     0.01307
0.0125     0.00947
0.0000     0.00000
0.0125     -0.00947
0.0250     -0.01307
0.0500     -0.01777
0.0750     -0.02100
0.1000     -0.02341
0.1500     -0.02673
0.2000     -0.02869
0.2500     -0.02971
0.3000     -0.03001
0.4000     -0.02902
0.5000     -0.02647
0.6000     -0.02282
0.7000     -0.01832
0.8000     -0.01312
0.9000     -0.00724
0.9500     -0.00403
1.0000     -0.00063];

X = airfoil_data(:,1);
Y = airfoil_data(:,2); % assign the y axis values from the   data points.

    N = 80; %number of points

for i = 1:(N/2)
    theta_i(i) = (pi/N)*(i-1);
    xupper(i) = 1-cos(theta_i(i));
end

for i = 1:18
    XU(i) = X(i);
    YU(i) = Y(i);
end
XU = XU';
YU = YU';
xupper = fliplr(xupper)';

Yupper = interp1(XU,YU,xupper,'spline');

for i = 1:(N/2)
    theta_i(i) = (pi/N)*(i-1);
    xlower(i) = 1-cos(theta_i(i));
end

for i = 1:17
    XL(i) = X(i+18);
    YL(i) = Y(i+18);
end
XL = XL';
YL = YL';
xlower = xlower';

Ylower = interp1(XL,YL,xlower,'spline');

X = [xupper;xlower];
Y = [Yupper;Ylower];

%user entered to modify endpoint
X(1) = 1;
X(end) = 1;
Y(1) = Y(1)/N;
Y(end) = Y(end)/N;