dropterm(MASS)
dropterm()所属R语言包：MASS
Try All One-Term Deletions from a Model
从模型中的所有尝试一个长期的缺失
译者：生物统计家园网 机器人LoveR
描述----------Description----------
Try fitting all models that differ from the current model by dropping a single term, maintaining marginality.
尝试适合所有型号的不同从目前的模式，放弃单一的长期，保持边缘化。
This function is generic; there exist methods for classes lm and glm and the default method will work for many other classes.
此功能是通用的;存在类lm和glm“默认的方法，将工作的许多其他类的方法。
用法----------Usage----------
dropterm (object, ...)
## Default S3 method:[默认方法]
dropterm(object, scope, scale = 0, test = c("none", "Chisq"),
k = 2, sorted = FALSE, trace = FALSE, ...)
## S3 method for class 'lm'
dropterm(object, scope, scale = 0, test = c("none", "Chisq", "F"),
k = 2, sorted = FALSE, ...)
## S3 method for class 'glm'
dropterm(object, scope, scale = 0, test = c("none", "Chisq", "F"),
k = 2, sorted = FALSE, trace = FALSE, ...)
参数----------Arguments----------
参数：object
A object fitted by some model-fitting function.
一个装有一些模型的拟合函数的对象。
参数：scope
a formula giving terms which might be dropped. By default, the model formula. Only terms that can be dropped and maintain marginality are actually tried.
一个公式，这可能会被丢弃的条款。默认情况下，模型的公式。实际上是试图可以下降，保持边缘化的唯一条件。
参数：scale
used in the definition of the AIC statistic for selecting the models, currently only for lm, aov and glm models. Specifying scale asserts that the residual standard error or dispersion is known.
AIC的统计定义用于选择的车型，目前仅用于lm，aov和glm模型。指定scale声称残留标准的错误或分散被称为“。
参数：test
should the results include a test statistic relative to the original model? The F test is only appropriate for lm and aov models, and perhaps for some over-dispersed glm models. The Chisq test can be an exact test (lm models with known scale) or a likelihood-ratio test depending on the method.
结果应该包括一个测试统计，相对于原始模型？ F检验是唯一适当的lm和aov车型，也许对于一些过度分散glm模型。 Chisq测试可以是一个准确的测试（lm已知规模的模型），或似然比检验方法。
参数：k
the multiple of the number of degrees of freedom used for the penalty. Only k = 2 gives the genuine AIC: k = log(n) is sometimes referred to as BIC or SBC.
多用于罚款的自由度数。只k = 2给人真正的工商行政管理机关：k = log(n)有时被称为BIC或单板。
参数：sorted
should the results be sorted on the value of AIC?
应AIC值进行排序的结果吗？
参数：trace
if TRUE additional information may be given on the fits as they are tried.
如果TRUE更多的信息，可配合给予他们试图。
参数：...
arguments passed to or from other methods. </table>
参数传递或其他方法。 </ TABLE>
Details
详情----------Details----------
The definition of AIC is only up to an additive constant: when appropriate (lm models with specified scale) the constant is taken to be that used in Mallows' Cp statistic and the results are labelled accordingly.
AIC的定义是最多只能添加剂常数：在适当的时候（lm指定规模的模型）不断采取锦葵“茂统计结果都标有相应。
值----------Value----------
A table of class "anova" containing at least columns for the change in degrees of freedom and AIC (or Cp) for the models. Some methods will give further information, for example sums of squares, deviances, log-likelihoods and test statistics.
类表"anova"至少列包含度的自由和AIC（或CP）为模型的变化。一些方法将给予进一步的信息，例如广场，心态，日志的可能性和测试统计款项。
参考文献----------References----------
Modern Applied Statistics with S. Fourth edition. Springer.
参见----------See Also----------
addterm, stepAIC
addterm，stepAIC
举例----------Examples----------
quine.hi <- aov(log(Days + 2.5) ~ .^4, quine)
quine.nxt <- update(quine.hi, . ~ . - Eth:Sex:Age rn)
dropterm(quine.nxt, test= "F")
quine.stp <- stepAIC(quine.nxt,
scope = list(upper = ~Eth*Sex*Age*Lrn, lower = ~1),
trace = FALSE)
dropterm(quine.stp, test = "F")
quine.3 <- update(quine.stp, . ~ . - Eth:Agern)
dropterm(quine.3, test = "F")
quine.4 <- update(quine.3, . ~ . - Eth:Age)
dropterm(quine.4, test = "F")
quine.5 <- update(quine.4, . ~ . - Agern)
dropterm(quine.5, test = "F")
house.glm0 <- glm(Freq ~ Infl*Type*Cont + Sat, family=poisson,
data = housing)
house.glm1 <- update(house.glm0, . ~ . + Sat*(Infl+Type+Cont))
dropterm(house.glm1, test = "Chisq")
转载请注明:出自 生物统计家园网(http://www.biostatistic.net)。
注：
注1：为了方便大家学习，本文档为生物统计家园网机器人LoveR翻译而成，仅供个人R语言学习参考使用，生物统计家园保留版权。
注2：由于是机器人自动翻译，难免有不准确之处，使用时仔细对照中、英文内容进行反复理解，可以帮助R语言的学习。
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发表于 2012-2-16 18:03:38
