Construct Design Matrices
Matrix creates a matrix from the given set of values. As.matrix attempts to turn its argument into a matrix. Is.matrix tests if its argument is a (strict) matrix. RDocumentation R Enterprise Training. Using the matrix function, we will create our first matrix in R. The basic syntax for creating a matrix in R is as follows: matrix (data, nrow, ncol, byrow, dimnames). The following syntax explains how to create an empty matrix in the R programming language by using the matrix function and the ncol and nrow arguments. Mymat matrix (ncol = 3, nrow = 0) # Applying matrix function mymat # Printing matrix to console # ,1 ,2 ,3 Have a look at the previous RStudio console output: It shows our matrix. https://ipdjvibrantstatsdepositmachine7playslot.peatix.com. R tries to simplify the matrix to a vector, if that’s possible. In this case, a single row is returned so, by default, this result is transformed to a vector. If a one-row matrix is simplified to a vector, the column names are used as names for the values.
model.matrix
creates a design (or model) matrix, e.g., by expanding factors to a set of dummy variables (depending on the contrasts) and expanding interactions similarly.Create Matrix In R
- Keywords
- models
Usage
Arguments
an object of an appropriate class. https://servicefree.mystrikingly.com/blog/lightning-jackpots-slot-machine. For the default method, a model formula or a
terms
object.1doc 1 1 2 – word processor for writer. a data frame created with
model.frame
. If another sort of object, model.frame
is called first.![Vectors Vectors](https://www.mssqltips.com/tipimages2/6514_r-services-subsetting-sql-server.022.png)
![Create Matrix In R Create Matrix In R](https://c1.staticflickr.com/5/4566/26834863909_e4c051d136_n.jpg)
a list, whose entries are values (numeric matrices,
function
s or character strings naming functions) to be used as replacement values for the contrasts
replacement function and whose names are the names of columns of data
containing factor
s.to be used as argument of
model.frame
if data
is such that model.frame
is called.further arguments passed to or from other methods.
Details
model.matrix
creates a design matrix from the description given in terms(object)
, using the data in data
which must supply variables with the same names as would be created by a call to model.frame(object)
or, more precisely, by evaluating attr(terms(object), 'variables')
. If data
is a data frame, there may be other columns and the order of columns is not important. Any character variables are coerced to factors. After coercion, all the variables used on the right-hand side of the formula must be logical, integer, numeric or factor.If
contrasts.arg
is specified for a factor it overrides the default factor coding for that variable and any 'contrasts'
attribute set by C
or contrasts
. Whereas invalid contrasts.arg
s have been ignored always, they are warned about since R version 3.6.0.In an interaction term, the variable whose levels vary fastest is the first one to appear in the formula (and not in the term), so in
~ a + b + b:a
the interaction will have a
varying fastest.By convention, if the response variable also appears on the right-hand side of the formula it is dropped (with a warning), although interactions involving the term are retained.
Value
The design matrix for a regression-like model with the specified formula and data.
There is an attribute
'assign'
, an integer vector with an entry for each column in the matrix giving the term in the formula which gave rise to the column. Value 0
corresponds to the intercept (if any), and positive values to terms in the order given by the term.labels
attribute of the terms
structure corresponding to object
.If there are any factors in terms in the model, there is an attribute
'contrasts'
, a named list with an entry for each factor. This specifies the contrasts that would be used in terms in which the factor is coded by contrasts (in some terms dummy coding may be used), either as a character vector naming a function or as a numeric matrix.References
Chambers, Four divine beasts. J. M. (1992) Data for models. Chapter 3 of Statistical Models in S eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole.
See Also
model.frame
, model.extract
, terms
sparse.model.matrix
from package Matrix for creating sparse model matrices, which may be more efficient in large dimensions.Aliases
- model.matrix
- model.matrix.default
- model.matrix.lm
Examples
library(stats)
# NOT RUN {ff <- log(Volume) ~ log(Height) + log(Girth)utils::str(m <- model.frame(ff, trees))mat <- model.matrix(ff, m)dd <- data.frame(a = gl(3,4), b = gl(4,1,12)) # balanced 2-wayoptions('contrasts') # typically 'treatment' (for unordered factors)model.matrix(~ a + b, dd)model.matrix(~ a + b, dd, contrasts = list(a = 'contr.sum'))model.matrix(~ a + b, dd, contrasts = list(a = 'contr.sum', b = contr.poly))m.orth <- model.matrix(~a+b, dd, contrasts = list(a = 'contr.helmert'))crossprod(m.orth) # m.orth is ALMOST orthogonal# invalid contrasts. ignored with a warning:stopifnot(identical( model.matrix(~ a + b, dd), model.matrix(~ a + b, dd, contrasts.arg = 'contr.FOO')))# }
Community examples
Create Matrix In R With Column And Row Names
API documentation