数学建模--插值和拟合实例
数学建模--插值和拟合实例求导数： - dV = gradient(V,t);
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较为准确的插值（形成一个平滑的曲线，可以看最后一问）：pp = csape(t0,dV);fdv = ppval(pp,tt0);plot(tt0,fdv);
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[*]拟合(polyfit和polyval)
a = [1 -6 5 3];x = -5:0.3:5;y = polyval(a,x);subplot(2,2,1);plot(x,y,'-');title('原图形');L = length(x);no = randn(1,L);%拟合b1 = polyfit(x,y+no,2);b2 = polyfit(x,y+no,3);b3 = polyfit(x,y+no,4);y1 = polyval(b1,x);y2 = polyval(b2,x);y3 = polyval(b3,x);subplot(2,2,2);plot(x,y1,'-');title('2图形');subplot(2,2,3);plot(x,y2,'-');title('3图形');subplot(2,2,4);plot(x,y3,'-');title('4图形');
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x = ;y0 = ;y = log(y0);b = polyfit(x,y,1);a = exp(b(2))k = (b(1)
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[*]插值
t = ;h = ;t0 = t./3600;V = pi/4*(57*0.3024).*h*0.3024;dV = -gradient(V,t0);no1 = find(h == -1);no2 = ;t0(no2) = [];dV(no2) = [];tt0 = 0:0.05:t0(end);pp = csape(t0,dV);fdv = ppval(pp,tt0);plot(tt0,fdv);
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