View source: R/prop_spline_est.R
prop_spline_est | R Documentation |
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, propensity spline basis, and treatment values.
prop_spline_est(Y, treat, covar_formula = ~ 1, covar_lin_formula = ~ 1, covar_sq_formula = ~ 1, data, e_treat_1 = NULL, degree = 1, wt = NULL, method = "same", spline_df = NULL, spline_const = 1, spline_linear = 1, spline_quad = 1)
Y |
is the the name of the outcome variable contained in |
treat |
is the name of the treatment variable contained in
|
covar_formula |
is the formula to describe the covariates needed
to estimate the constant term:
|
covar_lin_formula |
is the formula to describe the covariates needed
to estimate the linear term, t:
|
covar_sq_formula |
is the formula to describe the covariates needed
to estimate the quadratic term, t^2:
|
data |
is a dataframe containing |
e_treat_1 |
a vector, representing the conditional expectation of
|
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 with no spline terms. If method = "different", then different sets of covariates can be used to estimate the constant, linear, and/or quadratic term. To use spline terms, it is necessary to set method = "different". covar_lin_formula and covar_sq_formula must be specified if method = "different". |
spline_df |
degrees of freedom. The default, spline_df = NULL, corresponds to no knots. |
spline_const |
is the number of spline terms to include when estimating the constant term. |
spline_linear |
is the number of spline terms to include when estimating the linear term. |
spline_quad |
is the number of spline terms to include when estimating the quadratic term. |
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 and spline basis functions derived from the propensity function component.
prop_spline_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. |
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.
Little, Roderick and An, Hyonggin (2004). ROBUST LIKELIHOOD-BASED ANALYSIS OF MULTIVARIATE DATA WITH MISSING VALUES. Statistica Sinica. 14: 949–968.
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
,
reg_est
, aipwee_est
, wtrg_est
,
etc. for other estimates.
t_mod
, overlap_fun
to prepare the data
for use in the different estimates.
## Example from Schafer (2015). example_data <- sim_data t_mod_list <- t_mod(treat = T, treat_formula = T ~ B.1 + B.2 + B.3 + B.4 + B.5 + B.6 + B.7 + B.8, data = example_data, treat_mod = "Normal") cond_exp_data <- t_mod_list$T_data full_data <- cbind(example_data, cond_exp_data) prop_spline_list <- prop_spline_est(Y = Y, treat = T, covar_formula = ~ B.1 + B.2 + B.3 + B.4 + B.5 + B.6 + B.7 + B.8, covar_lin_formula = ~ 1, covar_sq_formula = ~ 1, data = example_data, e_treat_1 = full_data$est_treat, degree = 1, wt = NULL, method = "different", spline_df = 5, spline_const = 4, spline_linear = 4, spline_quad = 4) sample_index <- sample(1:1000, 100) plot(example_data$T[sample_index], example_data$Y[sample_index], xlab = "T", ylab = "Y", main = "propensity spline estimate") abline(prop_spline_list$param[1], prop_spline_list$param[2], lty = 2, col = "blue", lwd = 2) legend('bottomright', "propensity spline estimate", lty = 2, bty = 'Y', cex = 1, col = "blue", lwd = 2) rm(example_data, prop_spline_list, sample_index)
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