---
title: "opl_lc_c"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{opl_lc_c}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
```

```{r setup}
library(OPL)
```

## Introduction

The `opl_lc_c` function implements ex-ante treatment assignment using as
    policy class a fixed-depth (1-layer) decision-tree at specific splitting
    variables and threshold values.

## Usage

opl_lc_c(make_cate_result,z,w,c1=NA,c2=NA,c3=NA)


### Arguments

- `make_cate_result`: A data frame containing input data, including a column named `my_cate`, representing conditional average treatment effects (CATE).
- `w`: A character string indicating the column name for treatment assignment (binary variable).
- `policy_constraints`: A list of constraints applied to the treatment assignment, such as budget limits or fairness constraints.

### Output

The function returns the input data frame augmented with:
- `treatment_assignment`: Binary indicator for treatment assignment based on policy learning.
- `policy_summary`: Summary statistics detailing the constrained optimization results.

Additionally, the function:
- Prints a summary of key results, including welfare improvements under the learned policy.
- Displays a visualization of the treatment allocation.

## Details

The function follows these steps:
1. Estimates the optimal policy assignment using a machine learning-based approach.
2. Incorporates policy constraints to balance fairness, budget, or other practical limitations.
3. Computes and reports key statistics, including constrained welfare gains and proportion of treated units.

## Example

```r
# Load example data
set.seed(123)
data_example <- data.frame(
  my_cate = runif(100, -1, 1),
  treatment = sample(0:1, 100, replace = TRUE)")

# Define policy constraints
constraints <- list(budget = 0.5)  # Example: treating at most 50% of units

# Run learning-based constrained policy assignment
result <- opl_lc_c(
  make_cate_result = data_example,
  w = "treatment",
  policy_constraints = constraints
)
```

## Interpretation of Results

- The printed summary provides insights into the policy assignment under constraints.
- The visualization illustrates the treatment allocation based on CATE estimates.

## References

- Athey, S., & Wager, S. (2021). Policy Learning with Observational Data. *Econometrica*, 89(1), 133–161.
- Cerulli, G. (2021). Improving econometric prediction by machine learning. *Applied Economics Letters*, 28(16), 1419-1425.
- Cerulli, G. (2022). Optimal treatment assignment of a learning-based constrained policy: empirical protocol and related issues. *Applied Economics Letters*. DOI: 10.1080/13504851.2022.2032577.
- Gareth, J., Witten, D., Hastie, D.T., & Tibshirani, R. (2013). *An Introduction to Statistical Learning: with Applications in R*. New York: Springer.
- Kitagawa, T., & Tetenov, A. (2018). Who Should Be Treated? Empirical Welfare Maximization Methods for Treatment Choice. *Econometrica*, 86(2), 591–616.

---

This vignette provides an overview of the `opl_lc_c` function and demonstrates its usage for learning-based constrained policy assignment. For further details, consult the package documentation.