% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/declare_estimator.R
\name{declare_estimator}
\alias{declare_estimator}
\alias{declare_estimators}
\alias{label_estimator}
\alias{method_handler}
\title{Declare estimator}
\usage{
declare_estimator(
  ...,
  handler = label_estimator(method_handler),
  label = "estimator"
)

declare_estimators(
  ...,
  handler = label_estimator(method_handler),
  label = "estimator"
)

label_estimator(fn)

method_handler(
  data,
  ...,
  .method = estimatr::lm_robust,
  .summary = tidy_try,
  model,
  model_summary,
  term = FALSE
)
}
\arguments{
\item{...}{arguments to be captured, and later passed to the handler}

\item{handler}{a tidy-in, tidy-out function}

\item{label}{a string describing the step}

\item{fn}{A function that takes a data.frame as an argument and returns a data.frame with the estimates, summary statistics (i.e., standard error, p-value, and confidence interval), and a term column for labeling coefficient estimates.}

\item{data}{a data.frame}

\item{.method}{A method function, e.g. lm or glm. By default, the method is the \code{\link[estimatr:lm_robust]{estimatr::lm_robust}} function from the estimatr package, which fits OLS regression and calculates robust and cluster-robust standard errors.}

\item{.summary}{A method-in data-out function to extract coefficient estimates or method summary statistics, such as \code{\link[broom:tidy]{broom::tidy}} or \code{\link[broom:glance]{broom::glance}}. By default, the \code{DeclareDesign} method summary function \code{\link{tidy_try}} is used, which first attempts to use the available tidy method for the method object sent to \code{method}, then if not attempts to summarize coefficients using the \code{coef(summary())} and \code{confint} methods. If these do not exist for the method object, it fails.}

\item{model}{Deprecated argument. Use \code{.method} instead.}

\item{model_summary}{Deprecated argument. Use \code{.summary} instead.}

\item{term}{Symbols or literal character vector of term that represent quantities of interest, i.e. Z. If FALSE, return the first non-intercept term; if TRUE return all term. To escape non-standard-evaluation use \code{!!}.}
}
\value{
A function that accepts a data.frame as an argument and returns a data.frame containing the value of the estimator and associated statistics.
}
\description{
Declares an estimator which generates estimates and associated statistics.

Use of \code{declare_test} is identical to use of \code{\link{declare_estimator}}. Use \code{declare_test} for hypothesis testing with no specific inquiry in mind; use \code{declare_estimator} for hypothesis testing when you can link each estimate to an inquiry. For example, \code{declare_test} could be used for a K-S test of distributional equality and \code{declare_estimator} for a difference-in-means estimate of an average treatment effect.
}
\details{
\code{declare_estimator} is designed to handle two main ways of generating parameter estimates from data.

In \code{declare_estimator}, you can optionally provide the name of an inquiry or an object created by \code{\link{declare_inquiry}} to connect your estimate(s) to inquiry(s).

The first is through \code{label_estimator(method_handler)}, which is the default value of the \code{handler} argument. Users can use standard method functions like lm, glm, or iv_robust. The methods are summarized using the function passed to the \code{summary} argument. This will usually be a "tidier" like \code{broom::tidy}. The default \code{summary} function is \code{tidy_try}, which applies a tidy method if available, and if not, tries to make one on the fly.

An example of this approach is:

\code{declare_estimator(Y ~ Z + X, .method = lm_robust, .summary = tidy, term = "Z", inquiry = "ATE")}

The second approach is using a custom data-in, data-out function, usually first passed to \code{label_estimator}. The reason to pass the custom function to \code{label_estimator} first is to enable clean labeling and linking to inquiries.

An example of this approach is:

\code{
my_fun <- function(data){ with(data, median(Y[Z == 1]) - median(Y[Z == 0])) }
}

\code{
declare_estimator(handler = label_estimator(my_fun), inquiry = "ATE")
}

\code{label_estimator} takes a data-in-data out function to \code{fn}, and returns a data-in-data-out function that first runs the provided estimation function \code{fn} and then appends a label for the estimator and, if an inquiry is provided, a label for the inquiry.
}
\examples{

# Setup for examples
design <-
  declare_model(
    N = 500,
    gender = rbinom(N, 1, 0.5),
    U = rnorm(N, sd = 0.25),
    potential_outcomes(Y ~ rbinom(
      N, 1, prob = pnorm(0.2 * Z + 0.2 * gender + 0.1 * Z * gender + U)
    ))
  ) +
  declare_inquiry(ATE = mean(Y_Z_1 - Y_Z_0)) +
  declare_sampling(S = complete_rs(N = N, n = 200)) +
  declare_assignment(Z = complete_ra(N = N, m = 100)) +
  declare_measurement(Y = reveal_outcomes(Y ~ Z))

run_design(design)

# default estimator is lm_robust with tidy summary
design_0 <-
  design +
  declare_estimator(Y ~ Z, inquiry = "ATE")

run_design(design_0)

# Linear regression using lm_robust and tidy summary
design_1 <-
  design +
  declare_estimator(
    formula = Y ~ Z,
    .method = lm_robust,
    .summary = tidy,
    term = "Z",
    inquiry = "ATE",
    label = "lm_no_controls"
  )

run_design(design_1)

# Use glance summary function to view model fit statistics
design_2 <-
  design +
  declare_estimator(.method = lm_robust,
                    formula = Y ~ Z,
                    .summary = glance)

run_design(design_2)

# Custom answer strategies
# A custom estimator should take data as an argument and return a data.frame
# with columns such as "estimate", "std.error", "p.value", "conf.low", "conf.high"
my_estimator <- function(data) {
  data.frame(estimate = mean(data$Y))
}

# Add a custom estimator to the design, wrapping it in `label_estimator()`
# in order to pass label and inquiry arguments

design_3 <-
  design +
  declare_inquiry(Y_bar = mean(Y)) +
  declare_estimator(handler = label_estimator(my_estimator),
                    label = "mean",
                    inquiry = "Y_bar")

run_design(design_3)

# Use `term` to select particular coefficients
design_4 <-
  design +
  declare_inquiry(difference_in_cates = mean(Y_Z_1[gender == 1] - Y_Z_0[gender == 1]) -
                    mean(Y_Z_1[gender == 0] - Y_Z_0[gender == 0])) +
  declare_estimator(Y ~ Z * gender,
                    term = "Z:gender",
                    inquiry = "difference_in_cates",
                    .method = lm_robust)

run_design(design_4)

if(require("broom")) {

  # Use glm from base R
  design_5 <-
    design +
    declare_estimator(Y ~ Z + gender,
                      family = "gaussian",
                      inquiry = "ATE",
                      .method = glm)

  run_design(design_5)

  # If we use logit, we'll need to estimate the average marginal effect with
  # marginaleffects::avg_slopes. We wrap this up in a function we'll pass to
  # .summary.

  if(require("marginaleffects")) {

    library(marginaleffects) # for predictions
    library(broom) # for tidy

    tidy_avg_slopes <- function(x) {
      tidy(avg_slopes(x))
    }

    design_6 <-
      design +
      declare_estimator(
        Y ~ Z + gender,
        .method = glm,
        family = binomial("logit"),
        .summary = tidy_avg_slopes,
        term = "Z"
      )

    run_design(design_6)

    # Multiple estimators for one inquiry

    design_7 <-
      design +
      declare_estimator(Y ~ Z,
                        .method = lm_robust,
                        inquiry = "ATE",
                        label = "OLS") +
      declare_estimator(
        Y ~ Z + gender,
        .method = glm,
        family = binomial("logit"),
        .summary = tidy_avg_slopes,
        inquiry = "ATE",
        term = "Z",
        label = "logit"
      )

    run_design(design_7)

  }

}
}
\seealso{
\code{\link[estimatr:lm_robust]{estimatr::lm_robust()}}, \code{\link[broom:reexports]{broom::glance()}}
}
