Answered

curve fitting toolbox for y=y0.exp((x0/x)^v) where data is known, but y0,x0 and v are unknown constants

Hi, Em, if fit as the function: y=y0.exp((x0/x)^v), then the result will be about： Root of Mean Square Error (RMSE): 9.39279339...

curve fitting toolbox for y=y0.exp((x0/x)^v) where data is known, but y0,x0 and v are unknown constants

Hi, Em, if fit as the function: y=y0.exp((x0/x)^v), then the result will be about： Root of Mean Square Error (RMSE): 9.39279339...

2 years ago | 1

Answered

Nonlinear regression with two variables

Hi, Dipon, post your y, T and pH data please, if possible.

Nonlinear regression with two variables

Hi, Dipon, post your y, T and pH data please, if possible.

2 years ago | 0

Answered

How can I solve this system of equation

Hi, VinceUgo, the eqn8 and eqn9 can be combined into one equation, so your problem become a system equation solving with eight e...

How can I solve this system of equation

Hi, VinceUgo, the eqn8 and eqn9 can be combined into one equation, so your problem become a system equation solving with eight e...

2 years ago | 0

Answered

Fitting data to an equation with complex part

lsqcurvefit is seneitive to initial start-values since it use local optimization algorithm, same as cftool, there is a GA toolbo...

Fitting data to an equation with complex part

lsqcurvefit is seneitive to initial start-values since it use local optimization algorithm, same as cftool, there is a GA toolbo...

2 years ago | 0

| accepted

Answered

Failure in initial objective function evaluation. FSOLVE cannot continue

You have three equations with three unknown parametrs, but initial start-values, you provide two only (x0=[1 1];), is this your ...

Failure in initial objective function evaluation. FSOLVE cannot continue

You have three equations with three unknown parametrs, but initial start-values, you provide two only (x0=[1 1];), is this your ...

2 years ago | 1

Answered

i need to solve 7 nonlinear equations with 7 unknows

refer the results below: Constant G x2 x1 x4 x3 x5 x6 x7 600 301.524350251906 299.992603098721 301.890052790606 305.9220213239...

i need to solve 7 nonlinear equations with 7 unknows

refer the results below: Constant G x2 x1 x4 x3 x5 x6 x7 600 301.524350251906 299.992603098721 301.890052790606 305.9220213239...

2 years ago | 0

Answered

Problems fitting couple differential equations to experimental data

Hi, if possible, upload your data (t, P and M) please

Problems fitting couple differential equations to experimental data

Hi, if possible, upload your data (t, P and M) please

2 years ago | 0

Answered

How to improve accuracy in fsolve?

There are multi-solutions with high enough accurancy, even given the range limition in [0, pi/2]: 1: a1: 0.996298496311242 a2...

How to improve accuracy in fsolve?

There are multi-solutions with high enough accurancy, even given the range limition in [0, pi/2]: 1: a1: 0.996298496311242 a2...

2 years ago | 0

Answered

Create a model to solve an energy balance

Hi, I get two solutions: No. 1 2 tg -328.861557610457 -549.471818197512 tm 1.72830356360143 -541.712011528394 hrpg -0.007275...

Create a model to solve an energy balance

Hi, I get two solutions: No. 1 2 tg -328.861557610457 -549.471818197512 tm 1.72830356360143 -541.712011528394 hrpg -0.007275...

2 years ago | 0

Answered

Fitting a profile to a Guassian Model

Hi, would you please upload your data file (dependent: alpha, independent variables: Temperature T, Pressure P, mass flow rate m...

Fitting a profile to a Guassian Model

Hi, would you please upload your data file (dependent: alpha, independent variables: Temperature T, Pressure P, mass flow rate m...

2 years ago | 0

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...

2 years 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...

2 years 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...

2 years 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...

2 years 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))...

2 years 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...

2 years 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.

2 years 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

2 years 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...

2 years 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...

2 years 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...

2 years 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...

2 years 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...

2 years 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...

2 years 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...

2 years 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...

2 years 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 years 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 years 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 years 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 years ago | 0