x0=Pp(1,:); %Pp第一行为横坐标
y0=Pp(2,:); %Pp第一行为横坐标
h1 = abs(diff(x0)) ;
h = [h1 h1(end)];
ht = h;
yapp1 = gradient(y0)./ht; %matlab数值近似
yapp2 = del2(y0)./ht; %matlab数值近似
k2 = abs(yapp2)./(1+yapp1.^2).^(3/2);
plot(k2)
title('曲率曲线')
[~,maxFlag] = max(k2); %曲率最大位置
x_max = x0(maxFlag);
y_max = y0(maxFlag);
%画出图像 标注曲率最大点
figure
plot(x0,y0,'.-');
hold on;
plot(x_max,y_max,'rp')
title('标注最大曲率点')
xlabel('log10((norm(B*Xk-L)))')
ylabel('log10((norm(Xk)))')