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chj787金蟲 (小有名氣)
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[求助]
matlab擬合求助
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用matlab擬合一個(gè)方程: y=(a+bx+cx^2+dx^3)exp(-bx) x=[0.8,0.85,0.9,0.94,1,1.1,1.14,1.144,1.146,1.148,1.149,1.15,1.151,1.152,1.153,1.157,1.25,1.3,1.35,1.4,1.45,1.5,1.55,1.6,1.65,1.7,1.75,1.8,1.85,1.9,1.95,2,2.05,2.1,2.15,2.2,2.25,2.3,2.35,2.4]; y=[129698.6607,81517.14907,48462.38869,30160.54842,12625.39888,830.7904906,0,2.343989057,8.695584894,18.42928479,24.54823752,31.4946096,39.26181681,47.84108015,57.22581538,102.7141275,687.9234793,3872.493796,7589.20011,11578.99871,15654.88623,19681.73873,23751.25051,27388.0944,30756.13673,33816.1486,36542.19252,38921.37873,40955.22819,42660.53072,44067.23581,45213.10408,46138.07991,46880.36067,47474.18002,47948.97387,48329.25318,48634.92208,48881.88591,49082.65691]; 變量:x,y 擬合常數(shù): a,b,c,d 求高手幫助!給出matlab擬合程序。 [ Last edited by chj787 on 2012-5-20 at 16:29 ] |
金蟲 (正式寫手)
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x=[0.8,0.85,0.9,0.94,1,1.1,1.14,1.144,1.146,1.148,1.149,1.15,1.151,1.152,1.153,1.157,1.25,1.3,1.35,1.4,1.45,1.5,1.55,1.6,1.65,1.7,1.75,1.8,1.85,1.9,1.95,2,2.05,2.1,2.15,2.2,2.25,2.3,2.35,2.4]; y=[129698.6607,81517.14907,48462.38869,30160.54842,12625.39888,830.7904906,0,2.343989057,8.695584894,18.42928479,24.54823752,31.4946096,39.26181681,47.84108015,57.22581538,102.7141275,687.9234793,3872.493796,7589.20011,11578.99871,15654.88623,19681.73873,23751.25051,27388.0944,30756.13673,33816.1486,36542.19252,38921.37873,40955.22819,42660.53072,44067.23581,45213.10408,46138.07991,46880.36067,47474.18002,47948.97387,48329.25318,48634.92208,48881.88591,49082.65691]; ybeta=inline('(beta(1)+beta(2)*x+beta(3)*x.^2+beta(4)*x.^3).*exp(-beta(2)*x)','beta','x'); beta=nlinfit(x,y,ybeta,[1e+004,0,-1e+004,1e+004]); a=beta(1); b=beta(2); c=beta(3); d=beta(4); yy=(a+b*x+c*x.^2+d*x.^3).*exp(-b*x); plot(x,yy,x,y,'*') 但是會顯示 Warning: The Jacobian at the solution is ill-conditioned, and some model parameters may not be estimated well (they are not identifiable). Use caution in making predictions.所以可能還需要進(jìn)一步手動優(yōu)化,我做你何時(shí)用nlinfit也經(jīng)常出現(xiàn)這個(gè)警告,期待有高手解答。 擬合結(jié)果是 3866678.20479525 2.55862906421524 -8281766.51676900 4642226.52606192 希望能幫到你 |
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昨天看到一個(gè)用MatLab演奏卡儂的 可以站短問問他 http://www.gaoyang168.com/bbs/viewthread.php?tid=4519096 |

金蟲 (小有名氣)
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