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Questions tagged [nonlinear-functions]

A function that does not validate the additivity or homogeneity properties is characterized as non-linear.

In mathematics, a linear function (or map) f(x) is one which satisfies both of the following properties:

  • Additivity or superposition: f(x + y) = f(x) + f(y)
  • Homogeneity: f(alpha * x) = alpha * f(x)

A function that does not confirm the above is characterized as non-linear.

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How to draw my function to plot with data in R

I have data about response time at web site according users that hit at the same time. For example: 10 users hit the same time have (average) response time 300ms 20 users -> 450ms etc I import the data in R and I make the plot from 2 columns data…
Abraham
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non linear curve fitting with log functions

I have a set of data points pair (y,x). I want to fit a function using the form y = c * x * log2(x) I want to find the value of c. Matlab lsqcurvefit is not working for this. It seems to be stuck in local optima. Any suggestions on how to do…
Aniket Chakrabarti
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Nonlinear parameters search

need to find a set of optimal parameters P of the system y = P(1)*exp(-P(2)*x) - P(3)*x where x and y are experimental values. I defined my function f = @(P) P(1)*exp(-P(2)*x) - P(3)*x and guess = [1, 1, 1] and tried P =…
matlab-oh-no
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Extract data from plot in r

I have made a plot using ggplot on R and using the function nls because it was a non linear regression, now I would like to extract data from the graph, specifically I would like to know the value of the 2 curves in the graph when the y value is 0,…
Khandar
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Mathematica, solving non linear system of equations with lot of equations and variables

I need to find a square matrix A satisfying the equation A.L.A = -17/18A -2(A.L.L + L.A.L + (L.L).A) + 3(A.L + L.A) -4L.L.L + 8L.L - 44/9L + 8/9*(ID) ,where L is a diagonal matrix L = {{2/3,0,0,0},{0,5/12,0,0},{0,0,11/12,0},{0,0,0,2/3}}. I can…
user3053271
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Non-linear equation MATLAB

I have no idea how I could solve this equation with matlab: f(1)=0.098253*x(1)-atan((tan(x(1))-tan(x(2)))/2)*0.531268-0.433015*x(2)-0.27994 f(2)=0.9951*x(1)-atan((tan(x(1))-tan(x(2)))/2)*0.12909+0.866022*x(2)-0.350005; I tryed with function = f and…
user3038589
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How to determine the Jacobian when solving a nonlinear system by Newton-Raphson method

I am trying to solve some nonlinear systems by Newton's method and the solution accuracy is very important to my problem. without using the symbolic computation softwares, how can I compute the Jacobian of a general nonlinear system of polynomials…
LCFactorization
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convert nonlinear symbolic equations to matrix in matlab

I know how to convert linear equations to matrix by using equationstomatrix function syms x y z; [A, b] = equationsToMatrix([x + y - 2*z == 0, x + y + z == 1, 2*y - z + 5 == 0], [x, y, z]) %solution of the equation set A = [ 1, 1, -2] [ 1, 1, …
user2874944
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Solving a nonlinear ODE 2. Order in Matlab numerically

I have a nonlinear-ODE of the second order with trigonometric functions such that I cannot formulate it depending of the second derivation. For example: ay'' + b arctan(y'') + cy' + dy=0 y'(0)=0, y''(0)=0 Without existence of a term like…
Caniko
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Fitting restricted cubic splines in a cox model

I'd like to investigate a presumed U-shaped association of some continuous risk factor with my disease of preference using Cox proportional hazards regression. So far, I've done this with R and the survival package like…
miura
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how to find non-linear equation parameters using a dataset

I got a dataset of 2 variable X and Y. I think these 2 variables are link by an equation as follow: Y(X) = a ( b + c * X^d)^e , I have a lot of observation Xi and Yi and I would like: 1) Define parameters c, d and e. 2) confirm my…
akasolace
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R - functions of an estimated vector and its covariance matrix

Given a estimates for a vector of variables x[1:3] and its covariance matrix V[1:3,1:3], I seek a utility that will apply linear or nonlinear functions to two or more variables, such as x[4] = x[1] + x[2] x[5] = x[4] / x[3]. The estimated values of…
Ray Czaplewski
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Solving an overdetermined non-linear system for 8 unknowns

I am wondering what my best approach is in the following scenario. I have 8 unknowns, however a virtually unlimited number of non-linear equations which makes the system over-determined. unknowns: U M V N J S W N equations: U*M + V * Catime1 – V*M –…
raincity1199
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How does MATLAB's ode45 handle highly coupled ODEs (where y' depends on x' and x' depends on y', etc.)?

If I have two sets of highly coupled ODEs such as: dy/dt = A*dx/dt + B*y + C*x dx/dt = D*dy/dt + E*y + F*x or if I have a system like: U = function(dy/dt) dy/dt = function(U,...) How would ode45 normally handle this? If I were to do the…
Kimusubi
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plot new values for best fit nonlinear curve

I have created the best fit for a non linear function. It seems to be working correctly: #define a function fncTtr <- function(n,d) (d/n)*((sqrt(1+2*(n/d))-1)) #fit dFit <-…
andreSmol
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