Failure in initial objective function evaluation. LSQCURVEFIT cannot continue.
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raw = xlsread('File', 2); % read in sheet number 2
Pc = raw(60:141, 1);
Sw = raw(60:141, 9);
plot(Sw,Pc,'ro')
F = @(x,xdata)1-x(1)*exp(-(x(2)/xdata)^(x(3)));
x0 = [3 6 0.6];
[x,resnorm,~,exitflag,output] = lsqcurvefit(F,x0,Sw,Pc)
I keep getting this error.
Error in Skelt_LS_Code (line 16)
[x,resnorm,~,exitflag,output] = lsqcurvefit(F,x0,Sw,Pc)
Caused by:
Failure in initial objective function evaluation. LSQCURVEFIT cannot continue.
Any help is appreciated. Thank you
采纳的回答
Walter Roberson
2020-1-6
F = @(x,xdata)1-x(1)*exp(-(x(2)./xdata).^(x(3)));
6 个评论
Thaer Ismail
2020-1-6
Walter Roberson
2020-1-6
Can you post your data file for us to test with?
Thaer Ismail
2020-1-7
Thi Na Le
2020-2-27
Dear @Walter Roberson, I have data and try to fit as below. could you please solve this problem?
xdata=...
[5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180];
ydata=...
[0.04178 0.081 0.09475 0.1157 0.1326 0.1468 0.1587 0.169 0.178 0.186 0.193 0.199 0.205 0.211 0.215 0.22 0.224 0.229 0.233 0.238 0.242 0.245 0.257 0.261 0.264 0.266 0.269 0.272 0.274 0.277 0.273 0.275];
fun=@(x,xdata)a0*(1+((4.5*x(1)*x(2)*xdata)/(5.5+x(2)*xdata)));
x0=[0.05 10^(4)];
[x,resnorm,~,exitflag,output] = lsqcurvefit(fun,x0,xdata,ydata);
But th e erro occur as:
Error in sample2 (line 7)
[x,resnorm,~,exitflag,output] = lsqcurvefit(fun,x0,xdata,ydata);
Caused by:
Failure in initial objective function evaluation. LSQCURVEFIT cannot continue.
Thi Na Le
2020-2-27
ydata in previous reply was wrong. this is modification:
a0=4;
xdata=...
[5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180];
ydata=...
[0.04178 0.081 0.09475 0.1157 0.1326 0.1468 0.1587 0.169 0.178 0.186 0.193 0.199 0.205 0.211 0.215 0.22 0.224 0.229 0.233 0.238 0.242 0.245 0.248 0.251 0.254 0.257 0.258 0.261 0.264 0.266 0.269 0.272 0.274 0.277 0.273 0.275];
fun=@(x,xdata)a0*(1+((4.5*x(1)*x(2)*xdata)/(5.5+x(2)*xdata)));
x0=[0.01 0.0001];
>> plot(xdata,ydata,'o')
>> x = lsqcurvefit(fun,x0,xdata,ydata)
Error using lsqcurvefit (line 262)
Function value and YDATA sizes are not equal.
Walter Roberson
2020-2-27
You need ./ instead of /
更多回答（1 个）
Alex Sha
2020-1-7
0 个投票
Hi，Thaer Ismail， which is your exact fit function: "ydata=1-x1*exp(-(x2/xdata)^x3)" or "ydata=1-x1*exp((-x2/xdata)^x3)" ?
if the former, take initial start values as:
x0 = [-23124 0.3 -2.2];
1 个评论
Thaer Ismail
2020-1-7
It is actually the former.
I tried the initial guesses that you graciously provided but still get a very bad fit.
Thank you.
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