Answered

How to fit complicated function with 3 fitting parameters using Least square regression

Hi, you may try to use "lsqcurvefit" command or curve fitting tool box (cftool), it is also better if you post data as well as k...

How to fit complicated function with 3 fitting parameters using Least square regression

Hi, you may try to use "lsqcurvefit" command or curve fitting tool box (cftool), it is also better if you post data as well as k...

4 days ago | 0

| accepted

Answered

Why is this not working

There are another five more solutions: No. x1 x2 x3 x4 x5 x6 x7 x8 x9 1 300 200 200 0 0.0447213595499958 -0.0447213595499958 3...

Why is this not working

There are another five more solutions: No. x1 x2 x3 x4 x5 x6 x7 x8 x9 1 300 200 200 0 0.0447213595499958 -0.0447213595499958 3...

15 days ago | 0

Answered

Fsolve complex results make no sense

Hi, Frederic Kluser, with your second case of Eq(9), I get the results below, all seem to be prefect: p: 1.79143003389998 p1_h...

Fsolve complex results make no sense

Hi, Frederic Kluser, with your second case of Eq(9), I get the results below, all seem to be prefect: p: 1.79143003389998 p1_h...

25 days ago | 0

Answered

Optimization of 9 unknown with 9 nonlinear constraints by fmincom

one inequality constraint is: x(1)-x(2)+x(3)-x(4)+x(5)-x(6)+x(7)-x(8)+x(9)<=0 (1) while one of equality constraint is: J*(x...

Optimization of 9 unknown with 9 nonlinear constraints by fmincom

one inequality constraint is: x(1)-x(2)+x(3)-x(4)+x(5)-x(6)+x(7)-x(8)+x(9)<=0 (1) while one of equality constraint is: J*(x...

28 days ago | 1

Answered

I am solving 20 nonlinear equation using fsolve to find 20 variables' value. But i previously know one of variable's value. That variable is x(17) in eqn F(17). x(17)=1200. Based on this fixed variable i want to find remaining variables' value.

The equation F(17) seems to be meanless: F(17)= (100e6*((0.5*(x(5)*x(6)+x(7)*x(8)))+(0.5*(x(11)*x(15)+x(12)*x(16))))/(-C*x(17))...

I am solving 20 nonlinear equation using fsolve to find 20 variables' value. But i previously know one of variable's value. That variable is x(17) in eqn F(17). x(17)=1200. Based on this fixed variable i want to find remaining variables' value.

The equation F(17) seems to be meanless: F(17)= (100e6*((0.5*(x(5)*x(6)+x(7)*x(8)))+(0.5*(x(11)*x(15)+x(12)*x(16))))/(-C*x(17))...

1 month ago | 0

Answered

How to guess initialization parameters for non-linear curve fitting with nlinfit?

Hi, Aindrila, guessing the initial start value is always a difficult task since the local optimization algorithms are adopted in...

How to guess initialization parameters for non-linear curve fitting with nlinfit?

Hi, Aindrila, guessing the initial start value is always a difficult task since the local optimization algorithms are adopted in...

1 month ago | 0

| accepted

Answered

using least square fit to find the best fit parameters

Hi， Annie， upload your data file please, if possible.

using least square fit to find the best fit parameters

Hi， Annie， upload your data file please, if possible.

1 month ago | 0

Answered

How to solve 3 non-linear equations with 3 unknowns?

One of numerical solution looks like: x: 4.49127153145489E-101 y: 0.0437692354838294 z: 867273686630772

How to solve 3 non-linear equations with 3 unknowns?

One of numerical solution looks like: x: 4.49127153145489E-101 y: 0.0437692354838294 z: 867273686630772

1 month ago | 0

Answered

How can I fit this data?

Hi, toon, how about the model function below: z = (p1+p2*x+p3*x^2+p4*y+p5*y^2)/(1+p6*x+p7*x^2+p8*x^3+p9*y+p10*y^2); where x: s...

How can I fit this data?

Hi, toon, how about the model function below: z = (p1+p2*x+p3*x^2+p4*y+p5*y^2)/(1+p6*x+p7*x^2+p8*x^3+p9*y+p10*y^2); where x: s...

1 month ago | 0

Answered

How do I find the coefficients of a function for a curve fit?

The below should be the best solution: Root of Mean Square Error (RMSE): 0.0255893453091926 Sum of Squared Residual: 0.0471466...

How do I find the coefficients of a function for a curve fit?

The below should be the best solution: Root of Mean Square Error (RMSE): 0.0255893453091926 Sum of Squared Residual: 0.0471466...

1 month ago | 0

Answered

Matlab curve fitting two equations simultaneously with common arguments

Hi, Liu, your fitting functions are overdeterminted, there are multi-solutions: 1: Root of Mean Square Error (RMSE): 0.1634941...

Matlab curve fitting two equations simultaneously with common arguments

Hi, Liu, your fitting functions are overdeterminted, there are multi-solutions: 1: Root of Mean Square Error (RMSE): 0.1634941...

1 month ago | 0

Answered

continuity of a fit function in different regions

Hi, the function below meets your requirements， with the derivative to be zero at x=1 y = p1+p2*(((x-p3)*(x+p4))^2)^p5; Root o...

continuity of a fit function in different regions

Hi, the function below meets your requirements， with the derivative to be zero at x=1 y = p1+p2*(((x-p3)*(x+p4))^2)^p5; Root o...

1 month ago | 0

Answered

lsqcurvefit not adjusting some parameters as expected

The best solution seems to be: Root of Mean Square Error (RMSE): 8.58712889537096E-5 Sum of Squared Residual: 1.50943288116718...

lsqcurvefit not adjusting some parameters as expected

The best solution seems to be: Root of Mean Square Error (RMSE): 8.58712889537096E-5 Sum of Squared Residual: 1.50943288116718...

1 month ago | 0

Answered

Fit multiple data with one mathmatical model/function

Hello, AHMED, your fit function is overdeterminted which will lead to multi-solutions, the parameter of "a1" is redundant: C=a1...

Fit multiple data with one mathmatical model/function

Hello, AHMED, your fit function is overdeterminted which will lead to multi-solutions, the parameter of "a1" is redundant: C=a1...

1 month ago | 1

Answered

How to fit a custom equation?

If don't care the type of fitting function, try the below function, much simple but with much better result: y = b1+b2*x^1.5+b3...

How to fit a custom equation?

If don't care the type of fitting function, try the below function, much simple but with much better result: y = b1+b2*x^1.5+b3...

1 month ago | 0

Answered

Fitting a sigmoid curve using curve fitting tool box

Hi, Hair, the quailty of your data seems to be bad for sigmoid type of function. If take the function like: y = y0+a/(1+exp(-(x...

Fitting a sigmoid curve using curve fitting tool box

Hi, Hair, the quailty of your data seems to be bad for sigmoid type of function. If take the function like: y = y0+a/(1+exp(-(x...

1 month ago | 1

| accepted

Answered

How can i solve the error "Reference to non-existent field 'xShape'. Error in finDiffEvalAndChkErr Error in finitedifferences'"

Hi, as my test, if c>0.367879, there is no solution for your equations.

How can i solve the error "Reference to non-existent field 'xShape'. Error in finDiffEvalAndChkErr Error in finitedifferences'"

Hi, as my test, if c>0.367879, there is no solution for your equations.

2 months ago | 0

Answered

Error fsolve undefined function or variable x.

taking initial start-values as: x0=[6 0.5 150]; will produce: x1: 5.96 x2: 7.50486851347978E-7 x3: 152.194203428967

Error fsolve undefined function or variable x.

taking initial start-values as: x0=[6 0.5 150]; will produce: x1: 5.96 x2: 7.50486851347978E-7 x3: 152.194203428967

2 months ago | 1

Answered

Designing an iterative algorithm for a nonlinear system of equations

There are two set of solutions: 1 x1: 0.256953706774553 x2: -399.382730699003 x3: 0.0102597835062331 Fevl: 9.92301206481...

Designing an iterative algorithm for a nonlinear system of equations

There are two set of solutions: 1 x1: 0.256953706774553 x2: -399.382730699003 x3: 0.0102597835062331 Fevl: 9.92301206481...

2 months ago | 0

Answered

Solving a system of 5 dependent non-linear equations

My pleasure, it is actually very challenging problem, hard to be solved by common software or algorithms.

Solving a system of 5 dependent non-linear equations

My pleasure, it is actually very challenging problem, hard to be solved by common software or algorithms.

2 months ago | 0

Answered

fsolve & linsqnonlin cant solve my equations

The unique stable results: x1: 0.231780000872077 x2: 0.040000000119062 x3: 0.508699999227432 x4: 0.00060000005989538 x5: 4....

fsolve & linsqnonlin cant solve my equations

The unique stable results: x1: 0.231780000872077 x2: 0.040000000119062 x3: 0.508699999227432 x4: 0.00060000005989538 x5: 4....

2 months ago | 0

Answered

Solving a system of 5 dependent non-linear equations

Hi, if vt = 0.0257, the solution should be: m: 512.891368076595 rsh: -1.08505661410065 rs: 3.40678689852078 io: 0.8568128664...

Solving a system of 5 dependent non-linear equations

Hi, if vt = 0.0257, the solution should be: m: 512.891368076595 rsh: -1.08505661410065 rs: 3.40678689852078 io: 0.8568128664...

2 months ago | 0

Answered

Solving a system of nonlinear equations with bounded variables

There are two solutions: 1: q_b: 0.305291000916417 q_v: 0.0179815487538954 q_lp: 0.237309452162523 y: 1.25168611470519 pr:...

Solving a system of nonlinear equations with bounded variables

There are two solutions: 1: q_b: 0.305291000916417 q_v: 0.0179815487538954 q_lp: 0.237309452162523 y: 1.25168611470519 pr:...

2 months ago | 0

Answered

Curve fitting with constraints

Hellow, Paul, if adding one more parameter in your fitting function, i.e. y = a*exp(b*x) + c*exp(d*x)+f Then: from y(0) = 0, w...

Curve fitting with constraints

Hellow, Paul, if adding one more parameter in your fitting function, i.e. y = a*exp(b*x) + c*exp(d*x)+f Then: from y(0) = 0, w...

2 months ago | 0

Answered

how to solve a system of non linear-equations

Hi, I get the solutions below: 1: r1: 0.0136978624480164 r2: -0.0529268624480211 c1: 23794.5028958407 c2: 1043438.64860562 ...

how to solve a system of non linear-equations

Hi, I get the solutions below: 1: r1: 0.0136978624480164 r2: -0.0529268624480211 c1: 23794.5028958407 c2: 1043438.64860562 ...

2 months ago | 0

Answered

No solution found when solving 3 non linear equations

Hi, all, how about the solutions below, from the numerical perspective： 1： x1: -5.21219473201765E21 x2: -0.279500437676178 x...

No solution found when solving 3 non linear equations

Hi, all, how about the solutions below, from the numerical perspective： 1： x1: -5.21219473201765E21 x2: -0.279500437676178 x...

2 months ago | 0

Answered

Multiple equations solving in MATLAB

Hi, Golam, post out your problem, we may try.

Multiple equations solving in MATLAB

Hi, Golam, post out your problem, we may try.

2 months ago | 1

Answered

8 nonlinear equations, 8 unknowns - little luck with fsolve/vpasolve

Hi, Alex Tekin, you may try some solvers or software package with the ability of global optimization, i.e. Baron, Lingo, 1stOpt....

8 nonlinear equations, 8 unknowns - little luck with fsolve/vpasolve

Hi, Alex Tekin, you may try some solvers or software package with the ability of global optimization, i.e. Baron, Lingo, 1stOpt....

2 months ago | 1

| accepted

Answered

Non-linear Multivariate regression using genetic algorithm

The GA toolbox in Matlab is not an ideal tool for curve fitting with the goal of global optimizatiom result. Refer the result be...

Non-linear Multivariate regression using genetic algorithm

The GA toolbox in Matlab is not an ideal tool for curve fitting with the goal of global optimizatiom result. Refer the result be...

2 months ago | 0

Answered

fminsearch for fitting a function to experimental data

There seem to be two sets of solutions: 1: Root of Mean Square Error (RMSE): 2.45406561689894 Sum of Squared Residual: 78.291...

fminsearch for fitting a function to experimental data

There seem to be two sets of solutions: 1: Root of Mean Square Error (RMSE): 2.45406561689894 Sum of Squared Residual: 78.291...

2 months ago | 0