Add weights to draws objects, with one weight per draw, for use in subsequent weighting operations. For reasons of numerical accuracy, weights are stored in the form of unnormalized log-weights (in a variable called .log_weight). See weights.draws() for details how to extract weights from draws objects.

weight_draws(x, weights, ...)

# S3 method for draws_matrix
weight_draws(x, weights, log = FALSE, ...)

# S3 method for draws_array
weight_draws(x, weights, log = FALSE, ...)

# S3 method for draws_df
weight_draws(x, weights, log = FALSE, ...)

# S3 method for draws_list
weight_draws(x, weights, log = FALSE, ...)

# S3 method for draws_rvars
weight_draws(x, weights, log = FALSE, ...)

Arguments

x

(draws) A draws object or another R object for which the method is defined.

weights

(numeric vector) A vector of weights of length ndraws(x). Weights will be internally stored on the log scale (in a variable called .log_weight) and will not be normalized, but normalized (non-log) weights can be returned via the weights.draws() method later.

...

Arguments passed to individual methods (if applicable).

log

(logicla) Are the weights passed already on the log scale? The default is FALSE, that is, expecting weights to be on the standard (non-log) scale.

Value

A draws object of the same class as x.

Examples

x <- example_draws()

# sample some random weights for illustration
wts <- rexp(ndraws(x))
head(wts)
#> [1] 0.12537521 0.51153003 0.43158989 0.01586271 1.98827365 1.42360646

# add weights
x <- weight_draws(x, weights = wts)

# extract weights
head(weights(x)) # defaults to normalized weights
#> [1] 2.943483e-04 1.200939e-03 1.013260e-03 3.724149e-05 4.667947e-03
#> [6] 3.342256e-03
head(weights(x, normalize=FALSE)) # recover original weights
#> [1] 0.12537521 0.51153003 0.43158989 0.01586271 1.98827365 1.42360646
head(weights(x, log=TRUE)) # get normalized log-weights
#> [1]  -8.130747  -6.724652  -6.894582 -10.198087  -5.367036  -5.701109

# add weights which are already on the log scale
log_wts <- log(wts)
head(log_wts)
#> [1] -2.0764444 -0.6703490 -0.8402795 -4.1437844  0.6872667  0.3531934

x <- weight_draws(x, weights = log_wts, log = TRUE)
# extract weights
head(weights(x))
#> [1] 2.943483e-04 1.200939e-03 1.013260e-03 3.724149e-05 4.667947e-03
#> [6] 3.342256e-03
head(weights(x, log=TRUE, normalize = FALSE)) # recover original log_wts
#> [1] -2.0764444 -0.6703490 -0.8402795 -4.1437844  0.6872667  0.3531934