---
title: "Getting Started"
output:
  rmarkdown::html_vignette:
    md_extensions: [
      "-autolink_bare_uris"
    ]
vignette: >
  %\VignetteIndexEntry{Getting Started}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---




``` r
library(CausalQueries)
library(dplyr)
library(knitr)
```

# 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"`.


``` r
# 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:


``` r
plot(xy_model)
```

![Simple model](a1xymodel-1.png)

**Simple summaries:** You can access a simple summary using `summary()`



``` r
summary(xy_model)
#> 
#> Causal statement: 
#> X -> Y
#> 
#> Nodal types: 
#> 
#> Nodal types for X:
#> 0  1
#> 
#> Nodal types for Y:
#> 00  10  01  11
#> 
#> Guide to interpreting nodal types for Y:
#> 
#>   index  interpretation
#> 1    *-  Y = * if X = 0
#> 2    -*  Y = * if X = 1
#> 
#> Number of nodal 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.



``` r
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):


``` r
iv_model <-
  iv_model |> set_restrictions(decreasing('Z', 'X'))
```

Here is an example of setting priors (see `?set_priors` for more):


``` r
iv_model <-
  iv_model |> set_priors(distribution = "jeffreys")
#> Altering all parameters.
```

**Simulation**: Data can be drawn from a model like this:


``` r
data <- make_data(iv_model, n = 4)

data |> kable()
```



|  Z|  X|  Y|
|--:|--:|--:|
|  0|  1|  1|
|  1|  0|  0|
|  1|  0|  1|
|  1|  1|  1|



# Update the model

**Updating**: Update using `update_model`. You can pass all `rstan` arguments to `update_model`.


``` r
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)
```

**Inspecting**: You can access the posterior distribution on model parameters directly thus:


``` r

xy_model |> grab("posterior_distribution") |>
  head() |> kable()
```



|       X.0|       X.1|      Y.00|      Y.10|      Y.01|      Y.11|
|---------:|---------:|---------:|---------:|---------:|---------:|
| 0.5237547| 0.4762453| 0.1948964| 0.0523208| 0.5664182| 0.1863645|
| 0.4261285| 0.5738715| 0.0597984| 0.1743038| 0.6544728| 0.1114249|
| 0.5796467| 0.4203533| 0.1538045| 0.1640282| 0.4844825| 0.1976849|
| 0.5133653| 0.4866347| 0.0667460| 0.1497083| 0.5849814| 0.1985644|
| 0.5559260| 0.4440740| 0.1106234| 0.1599240| 0.6523280| 0.0771246|
| 0.5738242| 0.4261758| 0.0211059| 0.3386846| 0.5650897| 0.0751198|



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:


``` r
xy_model |>
  query_model("Y[X=1] > Y[X=0]",
              using = c("priors", "posteriors"))
#> 
#> Causal queries generated by query_model (all at population level)
#> 
#> |label           |using      |  mean|    sd| cred.low| cred.high|
#> |:---------------|:----------|-----:|-----:|--------:|---------:|
#> |Y[X=1] > Y[X=0] |priors     | 0.249| 0.195|    0.009|     0.705|
#> |Y[X=1] > Y[X=0] |posteriors | 0.529| 0.102|    0.313|     0.705|
```

This query asks the probability that $Y(1)> Y(0)$.

Examples of *conditional* queries:


``` r
xy_model |>
  query_model("Y[X=1] > Y[X=0] :|: X == 1 & Y == 1", using = c("priors", "posteriors"))
#> 
#> Causal queries generated by query_model (all at population level)
#> 
#> |label                                 |using      |  mean|    sd| cred.low| cred.high|
#> |:-------------------------------------|:----------|-----:|-----:|--------:|---------:|
#> |Y[X=1] > Y[X=0] given X == 1 & Y == 1 |priors     | 0.499| 0.283|    0.023|     0.970|
#> |Y[X=1] > Y[X=0] given X == 1 & Y == 1 |posteriors | 0.751| 0.134|    0.479|     0.978|
```

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:


``` r
xy_model |>
  query_model("Y[X=1] > Y[X=0] :|: Y[X=1] != Y[X=0]",
              using = c("priors", "posteriors"))
#> 
#> Causal queries generated by query_model (all at population level)
#> 
#> |label                                  |using      |  mean|   sd| cred.low| cred.high|
#> |:--------------------------------------|:----------|-----:|----:|--------:|---------:|
#> |Y[X=1] > Y[X=0] given Y[X=1] != Y[X=0] |priors     | 0.492| 0.29|    0.027|     0.974|
#> |Y[X=1] > Y[X=0] given Y[X=1] != Y[X=0] |posteriors | 0.809| 0.09|    0.648|     0.980|
```

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:



``` r
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)

batch_queries |> kable(digits = 2, caption = "tabular output")
```



Table: tabular output

|label                            |query           |given            |using      |case_level | mean|   sd| cred.low| cred.high|
|:--------------------------------|:---------------|:----------------|:----------|:----------|----:|----:|--------:|---------:|
|ATE                              |Y[X=1] - Y[X=0] |-                |priors     |FALSE      | 0.00| 0.31|    -0.64|      0.63|
|ATE                              |Y[X=1] - Y[X=0] |-                |posteriors |FALSE      | 0.39| 0.09|     0.21|      0.56|
|Positive effect given any effect |Y[X=1] > Y[X=0] |Y[X=1] != Y[X=0] |priors     |FALSE      | 0.50| 0.29|     0.02|      0.97|
|Positive effect given any effect |Y[X=1] > Y[X=0] |Y[X=1] != Y[X=0] |posteriors |FALSE      | 0.81| 0.09|     0.65|      0.98|



``` r
batch_queries |> plot()
```

![Simple query](a1batchplot-1.png)
