Questions tagged [piecewise-linear]
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78 questions
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Can a two-segment fixed-effects model be combined with only one random linear slope on the underlying time variable (given only 3 timepoints)?
I’m analyzing longitudinal data with three timepoints:
Time 0 = baseline
Time 12 = post-treatment
Time 24 = follow-up
Because the treatment occurs at Time 12, I’m modeling a potential change in ...
2
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0
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87
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Piecewise SEM with multilevel time series and unequal sample sizes — is mixing datasets per submodel OK?
I’m fitting a piecewise SEM where the response is observed at the plot × year level, but several endogenous predictors are measured once per site × year. I fit each submodel at the level of its ...
- 209
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1
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102
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Piecewise SEM with mixed resolutions: year-level environment, plot-level biota — how to avoid pseudo-replication and handle autocorrelation?
I’m fitting a piecewise SEM to understand drivers of a grass species' productivity. My data span ~20 years at a single location. Two variables are plot-level (3 plots) that were repeatedly sampled:
• ...
- 209
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63
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Standard Error of fitted value at breakpoint (segmented regression)
I am currently using the "segmented.lm" function to detect a change point in my data. At this stage I am trying to figure out how to derive the SE of the y value of the corresponding change ...
- 433
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Is there a statistical analysis that can be used in R to assess significant differences between regions of a curve?
I would like to know if there is a statistical analysis to determine differences between regions of a curve/regression across two treatments. I know there are several statistical analyses for ...
- 83
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1
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168
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Manual specification of knots vs bs() for Piecewise regression
I am learning how to specify and plot piecewise regressions and have encountered a confusing situation. Namely, I have specified the knot for a piecewise regression using 2 methods: (1) manual and (2) ...
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3
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Understanding spline transformation and regression coefficients
I do not understand properly what a spline does even in a simple situation of a piecewise regression, and I need some help. Consider the following basic example:
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265
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How does Multivariate Adaptive Regression Splines (MARS) consider the minimum number of observations between knots in the forward pass?
I try to explain my question with a simple example.
Let's say we have two variables $x_1$ and $x_2$. At the first two stages of the forward pass, effects of $x_1$ with a knot at $a_1$ and $x_2$ with a ...
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0
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77
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Custom contrasts in piecewise mixed effects models
I have longitudinal data from a two-group RCT in which the primary outcome was assessed at baseline, each week during the intervention, post-test and 5-month follow-up (6 times total). I am modeling ...
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2
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356
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How to combine two linear models?
I am trying to predict housing prices using as few variables as possible. One way that yielded the best results so far is splitting the data into two data-sets ($houses < 100m^2$ and $houses >= ...
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How to model suspected piecewise-linear data with a lasso GLM
My data consist ~130 observations. Each observation has several thousand features (including many collinear or otherwise useless features) and a position along a single spatial dimension. Some sets of ...
- 83
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596
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Fitting multiple piecewise linear regression model (with hinges)
I am trying to fit a multiple piecewise linear regression model, where I coerce the model to have the exact terms I want.
For example, let's say I want to fit the exact model below, with predictors $...
- 153
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1
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165
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Fitting a segmented regression with two zero boundary constraints
I am having trouble with this segmented regression as it requires two constraints and so far I have only treated single constraints.
Here is an example of some data I am trying to fit:
...
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10
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1
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Difference between Spline and Piecewise Regression
I was looking for the difference between spline regression and piecewise regression. Can someone please explain it to me? Also, if someone can provide me good reference on these 2 topics, with ...
- 277
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99
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Including intercept terms in piecewise linear programming
I am hoping to get some help in understanding whether the intercept terms are required in the objective function for piecewise linear programming (using the below code).
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