reg_est {causaldrf} R Documentation

## The regression prediction estimator

### Description

This method estimates the linear or quadratic parameters of the ADRF by estimating a least-squares fit on the basis functions which are composed of combinations of the covariates and treatment values.

### Usage

reg_est(Y,
treat,
covar_formula,
covar_lin_formula = NULL,
covar_sq_formula = NULL,
data,
degree,
wt = NULL,
method = "same")


### Arguments

 Y is the the name of the outcome variable contained in data. treat is the name of the treatment variable contained in data. covar_formula is the formula to describe the covariates needed to estimate the constant term: ~ X.1 + ..... Can include higher order terms or interactions. i.e. ~ X.1 + I(X.1^2) + X.1 * X.2 + ..... Don't forget the tilde before listing the covariates. covar_lin_formula is the formula to describe the covariates needed to estimate the linear term, t: ~ X.1 + ..... Can include higher order terms or interactions. i.e. ~ X.1 + I(X.1^2) + X.1 * X.2 + ..... Don't forget the tilde before listing the covariates. covar_sq_formula is the formula to describe the covariates needed to estimate the quadratic term, t^2: ~ X.1 + ..... Can include higher order terms or interactions. i.e. ~ X.1 + I(X.1^2) + X.1 * X.2 + ..... Don't forget the tilde before listing the covariates. data is a dataframe containing Y, treat, and X. degree is 1 for linear and 2 for quadratic outcome model. wt is weight used in lsfit for outcome regression. Default is wt = NULL. method is "same" if the same set of covariates are used to estimate the constant, linear, and/or quadratic term. If method = "different", then different sets of covariates can be used to estimate the constant, linear, and/or quadratic term. covar_lin_formula and covar_sq_formula must be specified if method = "different".

### Details

This function estimates the ADRF by the method described in Schafer and Galagate (2015) that fits an outcome model using a function of the covariates.

### Value

reg_est returns an object of class "causaldrf_lsfit", a list that contains the following components:

 param the estimated parameters. out_mod the result of the outcome model fit using lsfit. call the matched call.

### References

Schafer, J.L., Galagate, D.L. (2015). Causal inference with a continuous treatment and outcome: alternative estimators for parametric dose-response models. Manuscript in preparation.

Schafer, Joseph L, Kang, Joseph (2008). Average causal effects from nonrandomized studies: a practical guide and simulated example. Psychological methods, 13.4, 279.

iptw_est, ismw_est, aipwee_est, wtrg_est, etc. for other estimates.

t_mod, overlap_fun to prepare the data for use in the different estimates.

### Examples

## Example from Schafer (2015).

example_data <- sim_data

reg_list <- reg_est(Y = Y,
treat = T,
covar_formula = ~ B.1 + B.2 + B.3 + B.4 + B.5 + B.6 + B.7 + B.8,
covar_lin_formula = ~ 1,
covar_sq_formula = ~ 1,
data = example_data,
degree = 1,
wt = NULL,
method = "same")

sample_index <- sample(1:1000, 100)

plot(example_data$T[sample_index], example_data$Y[sample_index],
xlab = "T",
ylab = "Y",
main = "regression estimate")

abline(reg_list$param[1], reg_list$param[2],
lty = 2,
col = "blue",
lwd = 2)

legend('bottomright',
"regression estimate",
lty = 2,
bty = 'Y',
cex = 1,
col = "blue",
lwd = 2)

rm(example_data, reg_list, sample_index)


[Package causaldrf version 0.4.2 Index]