Matlab Interp2外推 [英] Matlab interp2 extrapolation

问题描述

我正在使用interp2进行2D插值.对于某些数据值， interp2命令返回NaN，因为其中一个尺寸在外部 由已知值向量定义的范围.

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.

可以用interp1命令推断.但是，是 有没有办法对interp2执行此操作?

Its possible to extrapolate with the interp1 command. However, Is there a way to do this for interp2?

谢谢

这是我使用interp2命令的代码:

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

推荐答案

嘿，请找到我的interp2代码，它只需要最大绑定值；

Hey please find my code for interp2 it just take max bound values;

function vq = Linear2dInterpWithClipExtrap(x,y,v,xq,yq);

    vq = interp2(x,y,v,xq,yq);

    [XMax, idxVMax] = max(x);
    [XMin, idxVMin] = min(x);

    idxMax = xq > XMax;
    idxMin = xq < XMin;
   if ~isempty(yq(idxMax));
    vq(idxMax) = LinearInterpWithClipExtrap(y,v(:,idxVMax),yq(idxMax));
   end
   if ~ isempty(yq(idxMin))
    vq(idxMin) = LinearInterpWithClipExtrap(y,v(:,idxVMin),yq(idxMin));
   end

   [YMax, idyVMax] = max(y);
    [YMin, idyVMin] = min(y);

    idyMax = yq > YMax;
    idyMin = yq < YMin;
   if ~isempty(xq(idyMax));
    vq(idyMax) = LinearInterpWithClipExtrap(x,v(idyVMax,:),xq(idyMax));
   end
   if ~ isempty(xq(idyMin));
    vq(idyMin) = LinearInterpWithClipExtrap(x,v(idyVMin,:),xq(idyMin));
   end



function vq = LinearInterpWithClipExtrap(x,v,xq);

    vq = interp1(x,v,xq);

    [XMax, idxVMax] = max(x);
    [XMin, idxVMin] = min(x);

    idxMax = xq > XMax;
    idxMin = xq < XMin;

    vq(idxMax) = v(idxVMax);
    vq(idxMin) = v(idxVMin

);

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