Select variables from a data frame whose names begin with a certain character string.
Select(data = list(), prefix = "y",
lhs = NULL, rhs = NULL, rhs2 = NULL, rhs3 = NULL,
as.character = FALSE, as.formula.arg = FALSE, tilde = TRUE,
exclude = NULL, sort.arg = TRUE)A data frame or a matrix.
A vector of character strings, or a logical.
If a character then
the variables chosen from data begin with the
value of prefix.
If a logical then
only TRUE is accepted and all the variables
in data are chosen.
A character string. The response of a formula.
A character string.
Included as part of the RHS a formula.
Set rhs = "0" to suppress the intercept.
Same as rhs but appended to its RHS,
i.e., paste0(rhs, " + ", rhs2, " + ", rhs3).
If used, rhs should be used first,
and then possibly rhs2
and then possibly rhs3.
Logical. Return the answer as a character string?
Logical. Is the answer a formula?
Logical.
If as.character and as.formula.arg
are both TRUE
then include the tilde in the formula?
Vector of character strings. Exclude these variables explicitly.
Logical. Sort the variables?
If as.character = FALSE and
as.formula.arg = FALSE then a matrix such
as cbind(y1, y2, y3).
If as.character = TRUE and
as.formula.arg = FALSE then a character string such
as "cbind(y1, y2, y3)".
If as.character = FALSE and
as.formula.arg = TRUE then a formula such
as lhs ~ y1 + y2 + y3.
If as.character = TRUE and
as.formula.arg = TRUE then a character string such
as "lhs ~ y1 + y2 + y3".
See the examples below.
By default, if no variables beginning the the value of prefix
is found then a NULL is returned.
Setting prefix = " " is a way of selecting no variables.
This is meant as a utility function to avoid manually:
(i) making a cbind call to construct
a big matrix response,
and
(ii) constructing a formula involving a lot of terms.
The savings can be made because the variables of interest
begin with some prefix, e.g., with the character "y".
# NOT RUN {
Pneumo <- pneumo
colnames(Pneumo) <- c("y1", "y2", "y3", "x2") # The "y" variables are response
Pneumo$x1 <- 1; Pneumo$x3 <- 3; Pneumo$x <- 0; Pneumo$x4 <- 4 # Add these
Select(data = Pneumo) # Same as with(Pneumo, cbind(y1, y2, y3))
Select(Pneumo, "x")
Select(Pneumo, "x", sort = FALSE, as.char = TRUE)
Select(Pneumo, "x", exclude = "x1")
Select(Pneumo, "x", exclude = "x1", as.char = TRUE)
Select(Pneumo, c("x", "y"))
Select(Pneumo, "z") # Now returns a NULL
Select(Pneumo, " ") # Now returns a NULL
Select(Pneumo, prefix = TRUE, as.formula = TRUE)
Select(Pneumo, "x", exclude = c("x3", "x1"), as.formula = TRUE,
lhs = "cbind(y1, y2, y3)", rhs = "0")
Select(Pneumo, "x", exclude = "x1", as.formula = TRUE, as.char = TRUE,
lhs = "cbind(y1, y2, y3)", rhs = "0")
# Now a 'real' example:
Huggins89table1 <- transform(Huggins89table1, x3.tij = t01)
tab1 <- subset(Huggins89table1,
rowSums(Select(Huggins89table1, "y")) > 0)
# Same as
# subset(Huggins89table1, y1 + y2 + y3 + y4 + y5 + y6 + y7 + y8 + y9 + y10 > 0)
# Long way to do it:
fit.th <-
vglm(cbind(y01, y02, y03, y04, y05, y06, y07, y08, y09, y10) ~ x2 + x3.tij,
xij = list(x3.tij ~ t01 + t02 + t03 + t04 + t05 + t06 + t07 + t08 +
t09 + t10 - 1),
posbernoulli.t(parallel.t = TRUE ~ x2 + x3.tij),
data = tab1, trace = TRUE,
form2 = ~ x2 + x3.tij + t01 + t02 + t03 + t04 + t05 + t06 + t07 + t08 +
t09 + t10)
# Short way to do it:
Fit.th <- vglm(Select(tab1, "y") ~ x2 + x3.tij,
xij = list(Select(tab1, "t", as.formula = TRUE,
sort = FALSE, lhs = "x3.tij", rhs = "0")),
posbernoulli.t(parallel.t = TRUE ~ x2 + x3.tij),
data = tab1, trace = TRUE,
form2 = Select(tab1, prefix = TRUE, as.formula = TRUE))
# }
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