MATLAB: Best matlab curve fitting functions

curve fitting

I have the following set of data:

x=[0 .1579 .3158 .4737 .6316 .7895 .9474 1.1053 1.2632 1.4211 1.5789 1.7368 1.8947 2.0526 2.2105 2.3684 2.5263 2.6842 2.8421 3]';
fx=[-.3637 .3164 -1.1263 -1.0672 .1076 1.8249 -.1899 1.3484 1.2583 3.2179 1.7378 3.6954 5.1611 6.7646 8.3733 8.1898 7.9968 10.2402 11.5248 16.6505]';

I have to fit a curve to this data, without using matlabs curve fitting toolbox. What are the best built in matlab functions to fit data like this?

Best Answer

There are three other functions you can use to fit nonlinear data: nlinfit (Statistics Toolbox), lsqcurvefit (Optimization Toolbox), and fminsearch (built-in MATLAB function).

Do you have a model you want to fit? (It looks like a noisy exponential function, but the process that created it dictates the model you fit to it.)

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MATLAB: How to calculate the area which located between curve and x-axis

Try this:

X = [1427.18976 1427.21024 1427.23072 1427.2512 1427.27168 1427.29216 1427.31264 1427.33312 1427.3536 1427.37408 1427.39456 1427.41504 1427.43552 1427.456];
Y = [2098.083 2231.598 1888.275 1945.497 3280.65 6656.64 7667.55 7286.07 7514.94 7324.23 7095.33 6980.91 7534.02 7400.52];
Z = trapz(X, Y)

MATLAB: Plot 4D….different contours

    do you mean this：
close all
clear,clc
x=[0  -1.73205161513813  -1.73210161662818
0  -1.73205161513813  0
0  -1.73205161513813  1.73210161662818
0  0  -1.73210161662818
0  0  0
0  0  1.73210161662818
0  1.73205161513813  -1.73210161662818
0  1.73205161513813  0
0  1.73205161513813  1.73210161662818
1.73210161662818  -1.73205161513813  -1.73210161662818
1.73210161662818  -1.73205161513813  0
1.73210161662818  -1.73205161513813  1.73210161662818
1.73210161662818  0  -1.73210161662818
1.73210161662818  0  0
1.73210161662818  0  1.73210161662818
1.73210161662818  1.73205161513813  -1.73210161662818
1.73210161662818  1.73205161513813  0
1.73210161662818  1.73205161513813  1.73210161662818
-1.73210161662818  -1.73205161513813  -1.73210161662818
-1.73210161662818  -1.73205161513813  0
-1.73210161662818  -1.73205161513813  1.73210161662818
-1.73210161662818  0  -1.73210161662818
-1.73210161662818  0  0
-1.73210161662818  0  1.73210161662818
-1.73210161662818  1.73205161513813  -1.73210161662818
-1.73210161662818  1.73205161513813  0
  -1.73210161662818  1.73205161513813  1.73210161662818];
     %Discretisation
     [x1,x2,x3]=deal(x(:,1),x(:,2),x(:,3));
x1fit = min(x1):.1:max(x1);
x2fit = min(x2):.1:max(x2);
x3fit = min(x3):.1:max(x3);
%Create the mesh  
[X1FIT,X2FIT] = meshgrid(x1fit,x2fit);
X3FIT=griddata(x1fit,x2fit,x3fit,X1FIT,X2FIT,'v4');
        %Evaluate the Y at the different locations
b=[898.619500324491 -49.6569643950741 0.957244154182521 -0.474633267533362 0.109261217410249 0.128653191020651 0.109267525885722 0.0654684323159314 0.155519747861591 -0.265812849175710];
YFIT = b(1)+b(2)*X1FIT+b(3)*X2FIT+b(4)*X3FIT+b(5)*(X1FIT.^2-1)+b(6)*X1FIT.*X2FIT+b(7)*(X2FIT.^2-1)+b(8)*X2FIT.*X3FIT+b(9)*(X3FIT.^2-1)+b(10)*X3FIT.*X1FIT;
surf(X1FIT,X2FIT,X3FIT,YFIT)

Best Answer

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MATLAB: How to calculate the area which located between curve and x-axis

MATLAB: Plot 4D….different contours

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