chain_state | R Documentation |
The chain state object provides cached access to target distribution log density and its gradient.
chain_state(position, momentum = NULL)
position |
Position component of chain state. |
momentum |
Momentum component of chain state. Optional. |
New chain state object. A list with entries
position
: A zero-argument function to evaluate position vector.
momentum
: A zero-argument function to evaluate momentum vector.
dimension
: A zero-argument function evaluate dimension of position and
momentum vectors.
update
: A function accepting arguments position
and momentum
for
updating the value of one or both of these state components.
copy
: A function for creating a copy of the state object including any
cached values.
log_density
: A function accepting argument target_distribution
for
evaluating the log density of the target distribution at the current
state, with caching of the value to avoid recomputation on subsequent
calls.
gradient_log_density
: A function accepting argument target_distribution
for evaluating the gradient of the log density of the target distribution
at the current state, with caching of the value to avoid recomputation on
subsequent calls.
state <- chain_state(c(0.1, -0.5))
target_distribution <- list(
log_density = function(x) -sum(x^2) / 2,
gradient_log_density = function(x) -x
)
state$gradient_log_density(target_distribution)
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