What package is GLHT in R?
multcomp
glht (Package: multcomp) : General Linear Hypotheses General linear hypotheses and multiple comparisons for parametric models, including generalized linear models, linear mixed effects models, and survival models.
What is the GLHT function in R?
glht returns an object of class glht , or of class glht. list if by is non- NULL . The latter is simply a list of glht objects, and the provided methods coef , confint , plot , summary , and vcov simply lapply the corresponding methods for class “glht” .
What is a GLHT?
General Linear Hypothesis Test (glht)
How do I cite Multcomp package in R?
Please cite the multcomp package by the following reference: Hothorn T, Bretz F, Westfall P (2008). “Simultaneous Inference in General Parametric Models.” Biometrical Journal, 50(3), 346–363.
Is Tukey a test?
The test statistic Tukey’s test is based on a formula very similar to that of the t-test. In fact, Tukey’s test is essentially a t-test, except that it corrects for family-wise error rate.
What is compact letter display?
Compact letter displays (CLDs) are letters that show which treatment groups are not significantly different by some statistical test. It is often desirable to include CLDs on graphs.
What are contrasts in statistics?
In statistics, a contrast is a linear combination of variables such that all the coefficients add up to zero. One way to think of it is as a set of weighted variables. In statistical tests, they define specific comparisons between variables. This might be scores, means or something else.
What is the Multcomp package in R?
multcomp: Simultaneous Inference in General Parametric Models. Simultaneous tests and confidence intervals for general linear hypotheses in parametric models, including linear, generalized linear, linear mixed effects, and survival models.
How do you cite Multcomp?
multcomp citation info. Please cite the multcomp package by the following reference: Hothorn T, Bretz F, Westfall P (2008). “Simultaneous Inference in General Parametric Models.” Biometrical Journal, 50(3), 346–363.
How to test a linear function in glht?
The generic method glht dispatches on its second argument (linfct). There are three ways, and thus methods, to specify linear functions to be tested: 1) The matrix of coefficients K can be specified directly via the linfct argument.
How is a symbolic description used in glht?
2) A symbolic description, either a character or expression vector passed to glht via its linfct argument, can be used to define the null hypothesis. A symbolic description must be interpretable as a valid R expression consisting of both the left and right hand side of a linear hypothesis.
Why does the glht function print a warning?
This is because the glht function is only evaluating differences among treatments, as specified. It prints a warning because the interaction term in your model implies that it can’t just compare means by level of treatment in a straightforward manner. I would suggest you add another column to your data set that combines site by treatment.
How are degrees of freedom used in glht?
An object of class glht, more specifically a list with elements optionally, the degrees of freedom when the exact t distribution is used for inference with print, summary, confint, coef and vcov methods being available. When called with linfct being an mcp object, an additional element focus is available storing the names of the factors under test.
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