contrasts(stats)
contrasts()所属R语言包：stats
Get and Set Contrast Matrices
获取和设置对比度矩阵
译者：生物统计家园网 机器人LoveR
描述----------Description----------
Set and view the contrasts associated with a factor.
设置和查看相关因素的对比。
用法----------Usage----------
contrasts(x, contrasts = TRUE, sparse = FALSE)
contrasts(x, how.many) <- value
参数----------Arguments----------
参数：x
a factor or a logical variable.
一个因素或一个逻辑变量。
参数：contrasts
logical. See "Details".
逻辑。见“详细资料”。
参数：sparse
logical indicating if the result should be sparse (of class dgCMatrix), using package Matrix.
逻辑表示，如果结果应该是稀疏的（类dgCMatrix），使用包Matrix。
参数：how.many
How many contrasts should be made. Defaults to one less than the number of levels of x. This need not be the same as the number of columns of value.
应多少对比。默认之一比x水平的数量少。这需要不相同作为value的列数。
参数：value
either a numeric matrix (or a sparse or dense matrix of a class extending dMatrix from package Matrix) whose columns give coefficients for contrasts in the levels of x, or the (quoted) name of a function which computes such matrices.
无论是数字矩阵（或疏或密矩阵的一类扩展dMatrix包Matrix）其列给各级x，或（引）名称对比系数这样的矩阵函数的计算。
Details
详情----------Details----------
If contrasts are not set for a factor the default functions from options("contrasts") are used.
如果对比一个因素设置默认功能从options("contrasts")使用。
A logical vector x is converted into a two-level factor with levels c(FALSE, TRUE) (regardless of which levels occur in the variable).
逻辑向量x转换成两个级别的因素与水平c(FALSE, TRUE)（不论水平的变量发生）。
The argument contrasts is ignored if x has a matrix contrasts attribute set. Otherwise if contrasts = TRUE it is passed to a contrasts function such as contr.treatment and if contrasts = FALSE an identity matrix is returned. Suitable functions have a first argument which is the character vector of levels, a named argument contrasts (always called with contrasts = TRUE) and optionally from R 2.10.0 a logical argument sparse.
参数contrasts如果x有一个矩阵contrasts属性设置将被忽略。否则，如果contrasts = TRUE它传递到一个对比的功能，如contr.treatment如果contrasts = FALSE身份返回矩阵。合适的功能，第一个参数，这是层次的特征向量，一个命名参数contrasts并有选择地从R 2.10.0逻辑参数contrasts = TRUE（sparse总是叫）。
If value supplies more than how.many contrasts, the first how.many are used. If too few are supplied, a suitable contrast matrix is created by extending value after ensuring its columns are contrasts (orthogonal to the constant term) and not collinear.
value如果提供比how.many对比，第一个how.many用于。如果提供太少，创建一个合适的对比度矩阵延长确保其列是对比（正交常数项），而不是共线后value。
参考文献----------References----------
Statistical models. Chapter 2 of Statistical Models in S eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole.
参见----------See Also----------
C, contr.helmert, contr.poly, contr.sum, contr.treatment; glm, aov, lm.
C，contr.helmert，contr.poly，contr.sum，contr.treatment;glm，aov，lm。
举例----------Examples----------
utils::example(factor)
fff <- ff[, drop=TRUE] # reduce to 5 levels.[减少到5级。]
contrasts(fff) # treatment contrasts by default[默认情况下，治疗的对比]
contrasts(C(fff, sum))
contrasts(fff, contrasts = FALSE) # the 5x5 identity matrix[5x5的单位矩阵]
contrasts(fff) <- contr.sum(5); contrasts(fff) # set sum contrasts[设置的总和对比]
contrasts(fff, 2) <- contr.sum(5); contrasts(fff) # set 2 contrasts[设置2对比]
# supply 2 contrasts, compute 2 more to make full set of 4.[提供2对比，计算2个全套4。]
contrasts(fff) <- contr.sum(5)[,1:2]; contrasts(fff)
## using sparse contrasts: % useful, once model.matrix() works with these :[稀疏的对比：％有用，的一次model.matrix（）＃使用这些工作：]
ffs <- fff
contrasts(ffs) <- contr.sum(5, sparse=TRUE)[,1:2]; contrasts(ffs)
stopifnot(all.equal(ffs, fff))
contrasts(ffs) <- contr.sum(5, sparse=TRUE); contrasts(ffs)
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。
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发表于 2012-2-16 19:08:52
