Make a model
Generating: To make a model you need to provide a
DAG statement to make_model. For instance
"X->Y""X -> M -> Y <- X" or"Z -> X -> Y <-> X".
# examples of models
xy_model <- make_model("X -> Y")
iv_model <- make_model("Z -> X -> Y <-> X")
Graphing: Once you have made a model you can inspect
the DAG:
plot of chunk unnamed-chunk-3
Simple summaries: You can access a simple summary
using summary()
summary(xy_model)
#>
#> Causal statement:
#> X -> Y
#>
#> Nodal types:
#> $X
#> 0 1
#>
#> node position display interpretation
#> 1 X NA X0 X = 0
#> 2 X NA X1 X = 1
#>
#> $Y
#> 00 10 01 11
#>
#> node position display interpretation
#> 1 Y 1 Y[*]* Y | X = 0
#> 2 Y 2 Y*[*] Y | X = 1
#>
#> Number of types by node:
#> X Y
#> 2 4
#>
#> Number of causal types: 8
#>
#> Note: Model does not contain: posterior_distribution, stan_objects;
#> to include these objects use update_model()
#>
#> Note: To pose causal queries of this model use query_model()
or you can examine model details using inspect().
Inspecting: The model has a set of parameters and a
default distribution over these.
xy_model |> inspect("parameters_df")
#>
#> parameters_df
#> Mapping of model parameters to nodal types:
#>
#> param_names: name of parameter
#> node: name of endogeneous node associated
#> with the parameter
#> gen: partial causal ordering of the
#> parameter's node
#> param_set: parameter groupings forming a simplex
#> given: if model has confounding gives
#> conditioning nodal type
#> param_value: parameter values
#> priors: hyperparameters of the prior
#> Dirichlet distribution
#>
#> param_names node gen param_set nodal_type given param_value priors
#> 1 X.0 X 1 X 0 0.50 1
#> 2 X.1 X 1 X 1 0.50 1
#> 3 Y.00 Y 2 Y 00 0.25 1
#> 4 Y.10 Y 2 Y 10 0.25 1
#> 5 Y.01 Y 2 Y 01 0.25 1
#> 6 Y.11 Y 2 Y 11 0.25 1
Tailoring: These features can be edited using
set_restrictions, set_priors and
set_parameters.
Here is an example of setting a monotonicity restriction (see
?set_restrictions for more):
iv_model <-
iv_model |> set_restrictions(decreasing('Z', 'X'))
Here is an example of setting priors (see ?set_priors
for more):
iv_model <-
iv_model |> set_priors(distribution = "jeffreys")
#> Altering all parameters.
Simulation: Data can be drawn from a model like
this:
data <- make_data(iv_model, n = 4)
data |> kable()
Update the model
Updating: Update using update_model.
You can pass all rstan arguments to
update_model.
df <-
data.frame(X = rbinom(100, 1, .5)) |>
mutate(Y = rbinom(100, 1, .25 + X*.5))
xy_model <-
xy_model |>
update_model(df, refresh = 0)
#>
#> SAMPLING FOR MODEL 'simplexes' NOW (CHAIN 1).
#> Chain 1:
#> Chain 1: Gradient evaluation took 1.5e-05 seconds
#> Chain 1: 1000 transitions using 10 leapfrog steps per transition would take 0.15 seconds.
#> Chain 1: Adjust your expectations accordingly!
#> Chain 1:
#> Chain 1:
#> Chain 1: Iteration: 1 / 2000 [ 0%] (Warmup)
#> Chain 1: Iteration: 200 / 2000 [ 10%] (Warmup)
#> Chain 1: Iteration: 400 / 2000 [ 20%] (Warmup)
#> Chain 1: Iteration: 600 / 2000 [ 30%] (Warmup)
#> Chain 1: Iteration: 800 / 2000 [ 40%] (Warmup)
#> Chain 1: Iteration: 1000 / 2000 [ 50%] (Warmup)
#> Chain 1: Iteration: 1001 / 2000 [ 50%] (Sampling)
#> Chain 1: Iteration: 1200 / 2000 [ 60%] (Sampling)
#> Chain 1: Iteration: 1400 / 2000 [ 70%] (Sampling)
#> Chain 1: Iteration: 1600 / 2000 [ 80%] (Sampling)
#> Chain 1: Iteration: 1800 / 2000 [ 90%] (Sampling)
#> Chain 1: Iteration: 2000 / 2000 [100%] (Sampling)
#> Chain 1:
#> Chain 1: Elapsed Time: 0.078 seconds (Warm-up)
#> Chain 1: 0.06 seconds (Sampling)
#> Chain 1: 0.138 seconds (Total)
#> Chain 1:
#>
#> SAMPLING FOR MODEL 'simplexes' NOW (CHAIN 2).
#> Chain 2:
#> Chain 2: Gradient evaluation took 1.2e-05 seconds
#> Chain 2: 1000 transitions using 10 leapfrog steps per transition would take 0.12 seconds.
#> Chain 2: Adjust your expectations accordingly!
#> Chain 2:
#> Chain 2:
#> Chain 2: Iteration: 1 / 2000 [ 0%] (Warmup)
#> Chain 2: Iteration: 200 / 2000 [ 10%] (Warmup)
#> Chain 2: Iteration: 400 / 2000 [ 20%] (Warmup)
#> Chain 2: Iteration: 600 / 2000 [ 30%] (Warmup)
#> Chain 2: Iteration: 800 / 2000 [ 40%] (Warmup)
#> Chain 2: Iteration: 1000 / 2000 [ 50%] (Warmup)
#> Chain 2: Iteration: 1001 / 2000 [ 50%] (Sampling)
#> Chain 2: Iteration: 1200 / 2000 [ 60%] (Sampling)
#> Chain 2: Iteration: 1400 / 2000 [ 70%] (Sampling)
#> Chain 2: Iteration: 1600 / 2000 [ 80%] (Sampling)
#> Chain 2: Iteration: 1800 / 2000 [ 90%] (Sampling)
#> Chain 2: Iteration: 2000 / 2000 [100%] (Sampling)
#> Chain 2:
#> Chain 2: Elapsed Time: 0.085 seconds (Warm-up)
#> Chain 2: 0.08 seconds (Sampling)
#> Chain 2: 0.165 seconds (Total)
#> Chain 2:
#>
#> SAMPLING FOR MODEL 'simplexes' NOW (CHAIN 3).
#> Chain 3:
#> Chain 3: Gradient evaluation took 1.5e-05 seconds
#> Chain 3: 1000 transitions using 10 leapfrog steps per transition would take 0.15 seconds.
#> Chain 3: Adjust your expectations accordingly!
#> Chain 3:
#> Chain 3:
#> Chain 3: Iteration: 1 / 2000 [ 0%] (Warmup)
#> Chain 3: Iteration: 200 / 2000 [ 10%] (Warmup)
#> Chain 3: Iteration: 400 / 2000 [ 20%] (Warmup)
#> Chain 3: Iteration: 600 / 2000 [ 30%] (Warmup)
#> Chain 3: Iteration: 800 / 2000 [ 40%] (Warmup)
#> Chain 3: Iteration: 1000 / 2000 [ 50%] (Warmup)
#> Chain 3: Iteration: 1001 / 2000 [ 50%] (Sampling)
#> Chain 3: Iteration: 1200 / 2000 [ 60%] (Sampling)
#> Chain 3: Iteration: 1400 / 2000 [ 70%] (Sampling)
#> Chain 3: Iteration: 1600 / 2000 [ 80%] (Sampling)
#> Chain 3: Iteration: 1800 / 2000 [ 90%] (Sampling)
#> Chain 3: Iteration: 2000 / 2000 [100%] (Sampling)
#> Chain 3:
#> Chain 3: Elapsed Time: 0.078 seconds (Warm-up)
#> Chain 3: 0.069 seconds (Sampling)
#> Chain 3: 0.147 seconds (Total)
#> Chain 3:
#>
#> SAMPLING FOR MODEL 'simplexes' NOW (CHAIN 4).
#> Chain 4:
#> Chain 4: Gradient evaluation took 1e-05 seconds
#> Chain 4: 1000 transitions using 10 leapfrog steps per transition would take 0.1 seconds.
#> Chain 4: Adjust your expectations accordingly!
#> Chain 4:
#> Chain 4:
#> Chain 4: Iteration: 1 / 2000 [ 0%] (Warmup)
#> Chain 4: Iteration: 200 / 2000 [ 10%] (Warmup)
#> Chain 4: Iteration: 400 / 2000 [ 20%] (Warmup)
#> Chain 4: Iteration: 600 / 2000 [ 30%] (Warmup)
#> Chain 4: Iteration: 800 / 2000 [ 40%] (Warmup)
#> Chain 4: Iteration: 1000 / 2000 [ 50%] (Warmup)
#> Chain 4: Iteration: 1001 / 2000 [ 50%] (Sampling)
#> Chain 4: Iteration: 1200 / 2000 [ 60%] (Sampling)
#> Chain 4: Iteration: 1400 / 2000 [ 70%] (Sampling)
#> Chain 4: Iteration: 1600 / 2000 [ 80%] (Sampling)
#> Chain 4: Iteration: 1800 / 2000 [ 90%] (Sampling)
#> Chain 4: Iteration: 2000 / 2000 [100%] (Sampling)
#> Chain 4:
#> Chain 4: Elapsed Time: 0.067 seconds (Warm-up)
#> Chain 4: 0.086 seconds (Sampling)
#> Chain 4: 0.153 seconds (Total)
#> Chain 4:
Inspecting: You can access the posterior
distribution on model parameters directly thus:
xy_model |> grab("posterior_distribution") |>
head() |> kable()
| 0.5832223 |
0.4167777 |
0.3364434 |
0.0289015 |
0.4300116 |
0.2046435 |
| 0.5197472 |
0.4802528 |
0.0094979 |
0.2362127 |
0.6339646 |
0.1203248 |
| 0.5027436 |
0.4972564 |
0.1816374 |
0.0558691 |
0.5533184 |
0.2091751 |
| 0.5175010 |
0.4824990 |
0.1201199 |
0.1788905 |
0.6102219 |
0.0907677 |
| 0.4523010 |
0.5476990 |
0.2520335 |
0.1362207 |
0.5555310 |
0.0562148 |
| 0.4981273 |
0.5018727 |
0.2911425 |
0.0848195 |
0.5178918 |
0.1061462 |
where each row is a draw of parameters.
Query the model
Arbitrary queries
Querying: You ask arbitrary causal queries of the
model.
Examples of unconditional queries:
xy_model |>
query_model("Y[X=1] > Y[X=0]",
using = c("priors", "posteriors"))
#>
#> Causal queries generated by query_model (all at population level)
#>
#> |query |using | mean| sd| cred.low| cred.high|
#> |:---------------|:----------|-----:|-----:|--------:|---------:|
#> |Y[X=1] > Y[X=0] |priors | 0.246| 0.193| 0.007| 0.707|
#> |Y[X=1] > Y[X=0] |posteriors | 0.523| 0.102| 0.317| 0.703|
This query asks the probability that \(Y(1)> Y(0)\).
Examples of conditional queries:
xy_model |>
query_model("Y[X=1] > Y[X=0] :|: X == 1 & Y == 1", using = c("priors", "posteriors"))
#> Error in parse(text = w_query): <text>:1:16: unexpected '|'
#> 1: q <- var4>var3:|
#> ^
This query asks the probability that \(Y(1)
> Y(0)\) given \(X=1\) and \(Y=1\); it is a type of “causes of effects”
query. Note that “:|:” is used to separate the main query element from
the conditional statement to avoid ambiguity, since “|” is reserved for
the “or” operator.
Queries can even be conditional on counterfactual quantities. Here
the probability of a positive effect given some effect:
xy_model |>
query_model("Y[X=1] > Y[X=0] :|: Y[X=1] != Y[X=0]",
using = c("priors", "posteriors"))
#> Error in parse(text = w_query): <text>:1:16: unexpected '|'
#> 1: q <- var6>var5:|
#> ^
Note that we use “:” to separate the base query from the condition
rather than “|” to avoid confusion with logical operators.
Output
Query output is ready for printing as tables, but can also be
plotted, which is especially useful with batch requests:
batch_queries <- xy_model |>
query_model(queries = list(ATE = "Y[X=1] - Y[X=0]",
`Positive effect given any effect` = "Y[X=1] > Y[X=0] :|: Y[X=1] != Y[X=0]"),
using = c("priors", "posteriors"),
expand_grid = TRUE)
#> Error in parse(text = w_query): <text>:1:16: unexpected '|'
#> 1: q <- var6>var5:|
#> ^
batch_queries |> kable(digits = 2, caption = "tabular output")
#> Error in eval(expr, envir, enclos): object 'batch_queries' not found
batch_queries |> plot()
#> Error in eval(expr, envir, enclos): object 'batch_queries' not found