Questions tagged [growth-model]
A growth model is a statistical model describing the growth of some population, be it in demographics, biology or otherwise. A well-known example is the logistic growth model.
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Latent growth curve model: The variance-covariance matrix of the estimated parameters (vcov) does not appear to be positive definite
I have run a latent growth curve model in R using lavaan and got the below warning. It would be good to hear suggestions on how to resolve this warning. The full output is below.
Note that I dummy-...
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Latent growth curve model with a continuous time-invariant covariate, multi-group or covariate model?
A Latent growth curve model with a time-invariant covariant can be specified with (at least) two ways, by using the multigroup model approach or the "regression approach".
By regression ...
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Effect of robust maximum likelihood estimator in structural equation modelling when data is normal?
I understand that when data are nonnormal robust maximum likelihood estimator can be used.
I'm wondering are there any disadvantages of using a robust maximum likelihood estimator when the data are ...
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Structural equation modeling (latent growth models): robust estimators to handle outliers?
Can I use robust estimators (e.g., "MLM" and "MLR"estimator lavaan options) to overcome outliers within my sample, or should I remove outliers?
For context, I am modelling the ...
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Lavaan growth model: to treat endogenous variable as ordinal or continuous
I am modelling the trajectories of scores on two cognitive tests (i.e., PAL and SOS) measured at four time points. To do this I am creating separate latent growth curve models for each cognitive test, ...
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Growth mixture model (hlme) from lcmm R package failing to converge - continuous timepoints?
I am currently creating a naive model, where the outcome is a continuous biological variable, and the time to measurement is a continuous time variable, defined as the time since the individual ...
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How to improve sample representativeness for longitudinal data collected via an online platform?
I am working with a longitudinal dataset exploring cognitive ageing (e.g., memory performance over time). Participants complete the study annually. Inclusion criteria for this study are 1) UK resident,...
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How does a latent variable's communality value (R-squared) afect the interpretation of a latent basis model?
I am running a latent basis model with 5 time points.
The model has 5 measures of 5 items that make a factor.
I ran the model with the folloing code(Mplus) ;
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Singular gradient errors in nls in R studio [closed]
I make fisheries work, and I need to estimate some parameters from the von Bertalanffy equation: Lt=Linf*(1-exp-K(t-t0)) here Linf, K, and t0 are the parameters that I want to estimate by FSA package ...
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Latent growth curve model - can I talk about an effect over time if I only have my outcome at the last timepoint?
I have a latent growth curve model with two variables. X (exposure to media) was measured at 5 time points over several years. Y (misinformation proneness) was measured only at the last time point (...
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How to interpret results of a latent basis analysis when the estimated lambda exceeds 1?
I have ran a latent basis analysis and got the results below.
S BY
AE1 0.000 0.000 999.000 999.000
AE2 0.714 0.185 3.867 0.000
AE3 ...
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Consequences for not estimating autocorrelated residuals in a growth curve model
I am fitting a second order growth model with 7 time points on Mplus.
When I estimate the model with autocorrelated residuals in it
the model will not run because of identification issues.
(when I ...
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Compare latent trajectories of two groups based on same model using SEM
I fit latent growth models using lavaan's growth() function in R. It looks like this:
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How to interpret the coefficients obtained from lme4, which has two co-variants in level 2?
I am doing a longitudinal study investigating how Y changed across time, with two time-invariant covariates at level two (between-person), one is Gender and ...
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What statistical analyses would you use to analyze the change across two time points, months apart?
I will be administering an early literacy assessment to preschoolers at 2 time points in the preschool year. I want to be able to examine the growth from point A to point B. I also wanted to ...
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Regressing slope on intercept in multivariate growth curve model
I'm running a multivariate growth model with two variables measured across 3 waves using lavaan/growth function.
Here's the model specification I'm using, with non-uniform time differences. Two ...
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fitting growth curves with nls singular gradient error [duplicate]
I'm having trouble fitting my model to a bacteria growth curve. I made a sample of my data below.
Code:
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Which method to use to scale/mean center a time-varying covariate in latent growth models (SEM)?
I have longitudinal data across several time points. At each time point, participants completed an online test up to 3 times (i.e., measurements were completed 1-3 times at each timepoint). The number ...
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Who formulated this Generalized Lotka-Volterra model? [closed]
In the introduction of this paper
Bifurcations in a predator–prey model with general logistic
growth and exponential fading memory
The authors claim
I didn't know that this model was well known.
Can ...
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Phonological errors in children
I have a data (ge3_ratio) with 86 observations measuring the ratio of phonological errors produced by children. The data was collected from spontaneous speech transcripts from 3 children aged 21 to 65 ...
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Decompose in factor rate of change
Let's say, we measure de asset concentration in a market with the ratio of the assets of the top 30 firms over the total assets in the market:
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nls() singular gradient matrix at initial parameter estimates error
I am trying to run a nls() to interpolate height growth of a tree given a series of samples, where each sample has a value of age, and height. I am using the Richards (1959) method:
$$
\textrm{Height}=...
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What method should I use to study population level growth and individual level growth?
I have a panel dataset which contains diameter measurement data for 88 trees obtained from a mapped stand in Duke Forest. The description of variables is:
Each tree is indexed by a unique ID (ID), and ...
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Latent growth model - Is it possible to fit this model on latent variables?
Would it be possible to fit latent growth curve model on latent variables instead of directly on the observed measures? Each latent variable would represent a latent construct (e.g., intelligence) at ...
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Fit Gompertz curve to growth data with decline phase
I measured the change in three traits (y1, y2, y3) over time (x). The three traits each reached a maximum at different times and then declined. I am interested in the phase until the max and would ...
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Power analysis and sample size for multilevel modeling growth curve (repeated measures)
I am aware that there are some useful threads already on free software for calculating sample sizes (see here). However I couldn't find anything specific to cross-classified MLM and repeated measures.
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How to code time for a piecewise growth model for experimental data
I have data from an experiment that records the effects of stress on blood pressure.
The study went as follows:
Participants had their blood pressure measured 4 times over ten minutes to assess their ...
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model logistic growth for two different bacteria over time
I have thw following data representing the number of bacteria detected in wastewater.
I would to model the growth overtime. Here is the data
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Growth curve analysis in R - time variable as a polynomial
I have narrowed down some specific questions and was advised that it's more appropriate to post them here than on stackoverflow
I'm building a growth curve model using lmer in R and I'm unsure about ...
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Growth curve modeling using lmer - how is it different from mixed effects regression?
EDIT: I'm realising time cannot be a random effect, is that right? Where does it fit with other fixed effects? Can time be a polynomial?
I am trying to set up a growth curve analysis using lmer, I ...
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Lagged predictors in irregular-time / asynchronous / time-unconstrained data
In growth curve modeling or other approaches, when time is constrained/synchronous/regular (i.e. panel/wave data; all observations occur synchronously), lagged prediction is trivial - simply add t-1 ...
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Latent Growth Modeling in Lavaan
Lavaan newbie here. I've been trying to specify a latent growth curve model in R for a few days now and been going through all the tutorials on the Lavaan website. The theoretical path is reasonably ...
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What transformations are permitted before a t-test for significance?
I have been using t-tests to test for significant differences between the means of populations. Specifically, I am trying to determine if revenues have increased significantly before and after a ...
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Using change in one variable (2 timepoints) to predict change in another variable (2 timepoints): latent change models?
I have two variables, both measured at two timepoints: before and after an experimental procedure.
I'm expecting that change in one variable from Time 1 to Time 2 will predict change in the other ...
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Statistical test for significance for plant growth over time. Is one-way ANOVA test appropriate?
I conducted an experiment where I had five different conditions and I measured plants growth. There were five trials for each condition. The plant's height was measured 8 times over 23 days. Can I do ...
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Examining growth rates and sex differences
I'm trying to figure out the best statistical test to use to understand my data. I've searched but haven't found anything super applicable. I'm working with an endangered animal species and have a lot ...
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Trying to fit a Latent Growth Model in R and I get the error " Could not compute standard errors! The information matrix could not be inverted."
I know that there are several other posts dealing with this same issue but I still can't seem to figure out why my model isn't working. I don't believe it is under identified because it is a fairly ...
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How to calculate exponential growth when the value is a percentage or probability?
I have a variable x that takes values between 1 and 0 (0<x<1). I want to calculate value of ...
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SEM warning message "WARNING: some estimated lv variances are negative" (Latent growth curve model)
When running a quadratic latent growth curve model (model_6 below) I get the following warning message: "...
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Vanishing partial derivative of least squares w.r.t. Verhulst growth parameter
The Verhulst growth model can be given as
$$P(t) = \frac{k}{1+ \left( \frac{k-P_0}{P_0} \right)\exp(-rt)}$$
where $P(t)$ is the population size at time $t$, $k$ is the carrying capacity, $P_0$ is the ...
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Growth curve model with structured missingness
I am attempting to fit a growth curve to data relating to school-aged children, 11-16. The data is collected at each year, across 5 years. Some individuals will have complete data (all 5 time points), ...
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How to compare replicated time series
I have several cell cultures at different salinities. I have 4 replicates at each salinity. You can get an example of the data, with 2 salinities, here:
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Analyzing the pattern in the growth of organisms using discrete data in R
I have data of the size of 200 individuals of a particular plant species. But the size was measured in an indirect way, counting the number of leaves (discrete data), monthly during a total of 14 ...
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Random slopes in a growth curve analysis
I want to test whether an intervention affects a continuous outcome over 5 possible time points. How do I decide whether to include random slopes? I want slope to be able to vary between intervention ...
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growth curve modeling for nominal and ordinal dependent variables
Is it possible to conduct growth curve modeling for nominal and ordinal dependent variables instead of a continuous variable? The aim is to investigate the nature of the growth trajectories and to ...
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Estimating growth rate from noisy data?
Let's say we want to estimate growth rate from noisy data. Due to noise, simple calculation will result in very poor estimates (calculating growth rates just exacerbates noise), so smoothing is needed....
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Laavan -Growth curve models with indirect effects
I have a latent growth model (growth curve model) with time-varying covariates.
I also want to to test for the possibility of indirect effects through the tine varying covariate.
Does Laavan allow for ...
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How to run a nls for multiple dependent variables?
I am unfamiliar with nls however after doing some research on the function it seems to be appropriate for my current analysis.
I am testing population declines over ...
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Can I include individuals with a single data point in a growth curve model?
I read that one of the main advantages of using a growth curve model is that it can handle missing data. Some of the participants in my study have data for only one time point, while most have data ...
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Orthogonal contrasts and the poly function in R: Interpreting the coefficients as "absolute" or "incremental" effects
in a growth curve like model, I try to test whether a trajectory (over time) is better described by a linear or quadratic trend. I fitted a linear mixed model (time nested in participants) and called ...
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