The polynomial tag has no wiki summary.
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215 views
Polynomial in linear regression
I am new to Regression and R. I know that polynomial functions are used when a regression model does not fit data (underfitting), but I want to know which degree of polynomial should be used? I also ...
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271 views
Recovering raw coefficients and variances from orthogonal polynomial regression
It seems that if I have a regression model such as $y_i \sim \beta_0 + \beta_1 x_i+\beta_2 x_i^2 +\beta_3 x_i^3$ I can either fit a raw polynomial and get unreliable results or fit an orthogonal ...
2
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40 views
Can the OLS residual variance suggest a polynomial relationship?
I am trying to figure out whether from the following graph of the OLS residuals that the linear relationship does not hold, and that probably a cubic relationship would do better? Since both in the ...
2
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67 views
Orthogonality of Hermite Polynomials
As we know probabilistic Hermite polynomials are orthogonal with respect to the weight function $\frac{1}{\sqrt{2 \pi}} e^{-x^2/2}$ (density of standard normal).
I have a distribution which is a ...
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40 views
Unit root test for ARIMA models
I have a slight confusion regarding seasonal models and which polynomial to use for conducting unit root tests.
Given a model:
$\phi(B)\Phi(B^s)\Delta^d\Delta^D_S X_t = \theta(B)\Theta(B^s)\epsilon ...
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26 views
nearest neighbors degrees of freedom
For polynomial fitting with a polynomial of degree $n$, we have $n$ degrees of freedom. Is there a similar concept for $k$ nearest neighbors? Is there any way to compare the degrees in general? I come ...
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100 views
Determining polynomial model coefficients forcing slope = 1 and intercept =0
I have two observational variables, Cobs and R, both subject to measurement error. I believe that a model of the form Cmod = a0 + a1*R + a2*R^2 + a3*R^3 would be a reasonable representation of the ...
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40 views
lm to lmer function tweaking
I have stolen and modified a snippet of code found off the internet from (http://www.r-bloggers.com/aic-bic-vs-crossvalidation/) which graphically depicts AIC and BIC values for different polynomial ...
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15 views
orthogonal contrast with an ordinal variable in gam
I am fitting a set of continuous and factor variables into a GAM. The factors are ordinal: they are levels of abundance of specific macroinvertebrates set as "none" (0% cover), "low" (>0-10% cover) ...
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98 views
SVM with svm and svmpath function
I am trying to compare the R functions svm (library: e1071) and svmpath (library svmpath).
...
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101 views
Model reduction - Backward elimination
The rule I use for reducing covariates (trimming) is as following:
Look at the highest order interaction. If that is not significant, drop it. If it is significant, stop.
If drop the highest order ...
