difeq_replicate {dde}  R Documentation 
Solve difference equations repeatedly
Description
Solve a replicate set of difference (or recurrence) equation by
iterating it a number of times. This is a wrapper around
difeq
that does not (yet) do anything clever to
avoid many allocations.
Usage
difeq_replicate(n, y, steps, target, parms, ..., n_out = 0L,
n_history = 0L, grow_history = FALSE, return_history = n_history > 0,
dllname = "", parms_are_real = TRUE, ynames = NULL, outnames = NULL,
return_by_column = TRUE, return_initial = TRUE, return_step = TRUE,
return_output_with_y = TRUE, restartable = FALSE,
return_minimal = FALSE, as_array = TRUE)
Arguments
n 
Number of replicates. It is an error to request zero replicates. 
y 
The initial state of the system. Must be either a
numeric vector or a 
steps 
A vector of steps to return the system at. The
first step is taken as step zero, and the solution will
be recorded at every other step in the vector. So to step a
system from time zero to times 1, 2, 3, ..., n use 0:n. Must be
integer values and will be passed through 
target 
The target function to advance. This can either be
an R function taking arguments 
parms 
Parameters to pass through to the difference function 
... 
Dummy arguments  nothing is allowed here, but this means that all further arguments must be specified by name (not order) so I can easily reorder them later on. 
n_out 
The number of output variables (in addition to the
difference equation variables). If given, then an R function
must return an attribute 
n_history 
The number of iterations of history to save during the simulation. By default, no history is saved. 
grow_history 
Logical indicating if history should be grown
during the simulation. If 
return_history 
Logical indicating if history is to be
returned. By default, history is returned if 
dllname 
Name of the shared library (without extension) to
find the function 
parms_are_real 
Logical, indicating if 
ynames 
Logical, indicating if the output should be named
following the names of the input vector 
outnames 
An optional character vector, used when

return_by_column 
Logical, indicating if the output should be
returned organised by column (rather than row). This incurs a
slight cost for transposing the matrices. If you can work with
matrices that are transposed relative to 
return_initial 
Logical, indicating if the output should
include the initial conditions. Specifying 
return_step 
Logical, indicating if a row (or column if

return_output_with_y 
Logical, indicating if the output
should be bound together with the returned matrix 
restartable 
Logical, indicating if the problem should be
restartable. If 
return_minimal 
Shorthand option  if set to 
as_array 
(Defunct) Logical, indicating if the output should
be converted into an array. If 
Details
It is not currently possible to replicate over a set of parameters at once yet; the same parameter set will be used for all replications.
The details of how replication is done here are all considered
implementation details and are up for change in the future  in
particular if the models are run in turn or simultaneously (and
the effect that has on the random number stream). Logic around
naming output may change in future too; note that varying names in
the y
here will have some unexpected behaviours.
Examples
# Here is a really simple equation that does a random walk with
# steps that are normally distributed:
rhs < function(i, y, p) y + runif(1)
y0 < 1
t < 0:10
p < 5
dde::difeq_replicate(10, y0, t, rhs, p)