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POmatlab curve fitting: restrictions on parameters
 

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  1. POmatlab curve fitting: restrictions on parameters
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    <p>I have 5 non-parametric models all with 5 to 8 parameters. This models are used to fit longitudinal data y(t) with t being time. Every datafile is fitted by all 5 models for comparison. The model itself cannot be altered. </p> <p>For fitting starting values are used and these are fitted into a lsqcurvefit model using a levenberg-marquardt algortihm. So I've written a script for several models and one function for curvefitting </p> <p>if i perform the curve fitting a lot of the starting values are wandering off to extreme values. This is the thing I want to avoid since these parameters should stay in the proximity off it's starting values and should only change between a well defined range or so that only curve fits within a standard deviation are included.Important to note here is that this restrictions should be imposed during the curve fitting (iterative numerization techique) and not afterwards. </p> <p>The function I've written to fit models into height:</p> <pre><code>% Fit a specific model for all valid persons try opts = optimoptions(@lsqcurvefit, 'Algorithm', 'levenberg-marquardt'); [personalParams,personalRes,personalResidual] = lsqcurvefit(heightModel,initialValues,personalData(:,1),personalData(:,2),[],[],opts); catch x=1; end </code></pre> <p>The function I've written for one of my models</p> <pre><code> elseif strcmpi(model,'jpss') % y = h_1(1-(1/(1+((t+0.75)^c_1/d_1)+((t+0.75)^c_2/d_2)+((t+0.75)^c_3/d_3))) % heightModel = @(params,ages) params(1).*(1-1./(1+((ages+0.75).^params(2))./params(3) + ((ages+0.75).^params(4))./params(5) + ((ages+0.75).^params(6))./params(7))); heightModel = @(params,ages) params(1).*(1-1./(1+(((ages+0.75)./params(3)).^params(2)) + (((ages+0.75)./params(5)).^params(4)) + ((ages+0.75)./params(7)).^params(6))); % Adapted 25/07 modelStrings = {'h1','c1','d1','c2','d2','c3','d3'}; % Define initial values if strcmpi('male',gender) initialValues = [174.8 0.6109 2.9743 3.614 9.88 22.393 13.59]; else initialValues = [162.7 0.6546 2.43 4.011 8.579 18.394 11.846]; end </code></pre> <p>What I would like to do:</p> <p>Is it possible to place restrictions on every startingvalue @initial values? Putting restrictions on lsqcurvefit wouldn't be a good idea I think since there are different models with different starting values and different ranges that are allowed.</p> <p>I had 2 things in my mind: 1. using range and place this between the initial values initialValues = [162.7 0.6546 2.43 4.011 8.579 18.394 11.846]` if range a1=[150,180]; range a2=[0.3,0.8] and so one</p> <ol> <li>place lb and ub restrictions seperatly on all my initialvalues between lsqcurvefit if Heightmodel='name model' initial value* 1.2 and lb = initial value* 0.8 </li> </ol> <p>Can someone give me some hints or pointers because I can't make it work. </p> <p>Thanks in advance</p> <p>Lucy </p> <p>Could somebody help me out </p>
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