# ddFixed: Auxiliary Functions for Fixed Effects

## Description

Functions used in formula of `ddhazard`

for time-invariant effects. `ddFixed_intercept`

is only used for the intercept.

## Usage

ddFixed(object)ddFixed_intercept(random_intercept = FALSE)

## Arguments

object

expression that would be used in formula. E.g. `x`

or `poly(x, degree = 3)`

.

random_intercept

`TRUE`

if a zero mean time-varying process
should be included at as an additional term. Only relevant in stationary
models. See the `type`

argument in `PF_EM`

.

## Examples

# NOT RUN {
# we can get a time-invariant effect of `x1` by
# }
# NOT RUN {
ddhazard(Surv(stop, event) ~ ddFixed(x1), data)
# }
# NOT RUN {
# all of the calls below will yield the same result with a time-invariant
# intercept:
# }
# NOT RUN {
ddhazard(Surv(stop, event) ~ ddFixed_intercept() + x1, data)
ddhazard(Surv(stop, event) ~ -1 + ddFixed_intercept() + x1, data)
# }