n=15;
x=-1:0.01:1;
y=(1+25*x.^2).^(-1);
xx=-1:2/n:1;
y1=interp1(x,y,xx,'linear'); %分段线性插值
y2=interp1(x,y,xx,'pchip');%分段三次Hermite插值
y3=interp1(x,y,xx,'spline');%三次样条函数插值
y4=interp1(x,y,xx,'nearest');%最近邻点插值
hold on;
plot(x,y);
plot(xx,y1,'k-');
plot(xx,y2,'ok');
plot(xx,y3,'ok-');
plot(xx,y4,'o');
hold off;
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