Extract term names from a fitted model object.
Arguments
- mod
A fitted model object, or a list or nested list of such objects.
- intercept
Logical, whether the intercept should be included.
- aliased
Logical, whether names of aliased terms should be included (see Details).
- list
Logical, whether names should be returned as a list, with all multi-coefficient terms grouped under their main term names.
- env
Environment in which to look for model data (used to construct the model frame). Defaults to the
formula()environment.
Details
Extract term names from a fitted model. Names of terms for which
coefficients cannot be estimated are also included if aliased = TRUE
(default). These may be terms which are perfectly correlated with other
terms in the model, so that the model design matrix is rank deficient.
Examples
# Term names from Shipley SEM
m <- shipley.sem
xNam(m)
#> $DD
#> [1] "(Intercept)" "lat"
#>
#> $Date
#> [1] "(Intercept)" "DD"
#>
#> $Growth
#> [1] "(Intercept)" "Date"
#>
#> $Live
#> [1] "(Intercept)" "Growth"
#>
xNam(m, intercept = FALSE)
#> $DD
#> [1] "lat"
#>
#> $Date
#> [1] "DD"
#>
#> $Growth
#> [1] "Date"
#>
#> $Live
#> [1] "Growth"
#>
# Model with different types of predictor (some multi-coefficient terms)
d <- data.frame(
y = rnorm(100),
x1 = rnorm(100),
x2 = as.factor(rep(c("a", "b", "c", "d"), each = 25)),
x3 = rep(1, 100)
)
m <- lm(y ~ poly(x1, 2) + x2 + x3, data = d)
xNam(m)
#> [1] "(Intercept)" "poly(x1, 2)1" "poly(x1, 2)2" "x2b" "x2c"
#> [6] "x2d" "x3"
xNam(m, aliased = FALSE) # drop term that cannot be estimated (x3)
#> [1] "(Intercept)" "poly(x1, 2)1" "poly(x1, 2)2" "x2b" "x2c"
#> [6] "x2d"
xNam(m, aliased = FALSE, list = TRUE) # names as list
#> $`(Intercept)`
#> [1] "(Intercept)"
#>
#> $`poly(x1, 2)`
#> [1] "poly(x1, 2)1" "poly(x1, 2)2"
#>
#> $x2
#> [1] "x2b" "x2c" "x2d"
#>