nonlinear regression

  1. E

    Jacabi Matrix of nonlinear regression model with more rows as observations

    I am wondering why the Jacobi matrix from my model estimated by matlab has three times more rows, as there are observations. I have estimated the nonlinear regression model in the added file by the following command in Matlab: options=optimset('MaxFunEvals', 10000, 'MaxIter', 10000, 'TolFun'...
  2. A

    Least squares estimate of alpha and beta

    My group have different opinions towards the following question: Find the least squares estimate of alpha and beta of the mechanistic growth model: Y=alpha*(1-beta*e^-x) using the following dataset. Y 1 1.1 1.39 1.55 1.63 1.86 1.98 X 0 0.1 0.5 0.8 1 2 4...
  3. A

    Can AIC values be combined?

    Hello! I have hunted far and wide on the net in an attempt to answer this. Essentially, I'm trying to combine two AIC scores from different parts of a single data set. I have two models (of the same type: nonlinear least squares fitting a growth curve to population data) that each predict...
  4. C

    Problem with nlme() convergence in a Monte Carlo simulation

    Hello. As part of a Monte Carlo simulation, I'm programming some model comparisons on generated data. The underlying relationship in the data is a two-parameter exponential curve (y=a*e^(bx)), and among the models being compared are hyperbolic (y=a/(1+bx)), and quadratic (y=b*(x-a)^2)...
  5. D

    Linear or non-linear regression model

    Hi, I have 20 independent variables and 1 dependent. I've used the stepwise method to determined what predictors are more significant compared to other predictors and I ended up with 10 statistically significant predictors. However, I am not sure how check if a nonlinear multiple...
  6. F

    problem with defining constraint in Nonlinear Regression

    Hi all I have a question. Is there any way to set a parameter to be greater than the other one as the constraint when we want to use nonlinear regression in SPSS? (in constraint part I just could determine the parameter to be greater than a specific number not another parameter) Thank you
  7. R

    Non-linear modelling with several variables including a categorical variable

    Hello everyone, I am trying to model some data regarding a predator prey interaction experiment (n=26) in R. Predation rate is my response variable and I have 4 explanatory variables: predator density (1,2,3,4 5), predator size, prey density (5,10,15,20,25,30) and prey type (3 categories). I...
  8. B

    Having problems with CATREG for big and small data sets and defining scaling level.

    0 down vote favorite I am facing with an interesting problem here. I have a data set containing mixed nature of independent variables (some are nominal, some are ordinal, some are scale). The dependent variable is ordinal. I thought if I use CATREG in SPSS then I am going to get only one...
  9. B

    How to test for and remedy multicollinearity in optimal scaling regression?

    I have a data set containing only categorical variables (both nominal and ordinal in nature). The dependent variable is also ordinal (with 4 categories). I was planning to run a categorical regression with optimal scaling instead of ordinal logistic regression aiming at obtaining a single beta...
  10. B

    R2 values for reduced major axis regression in spss

    Good day! I need to do reduced major axis regression in SPSS, and I am using the Constrained Non-Linear Regression procedure for this (my syntax looks something like this): MODEL PROGRAM A=1 B=1. COMPUTE PRED=A+B*X. COMPUTE LOSS=((Y-PRED)**2)/ABS(B). CNLR Y /LOSS=LOSS. with Y as...
  11. F

    [Error] length of 'dimnames' [2] not equal to array extent

    Hello all, I'm trying to use the user-created multinomRob to make some models for my data. While documentation for that function is great and I think I'm using it correctly, I'm getting the following error when I try to use my dataframes. data <- read.csv("data.csv", header=FALSE) subj1...