txshift
Efficient Estimation of the Causal Effects of Stochastic Interventions
Authors: Nima Hejazi and David Benkeser
txshift
?The txshift
R package is designed to provide facilities for the
construction of efficient estimators of a causal parameter defined as
the counterfactual mean of an outcome under stochastic mechanisms for
treatment assignment (Dı́az and van der Laan 2012). txshift
implements
and builds upon a simplified algorithm for the targeted maximum
likelihood (TML) estimator of such a causal parameter, originally
proposed by Dı́az and van der Laan (2018), and makes use of analogous
machinery to compute an efficient one-step estimator (Pfanzagl and
Wefelmeyer 1985). txshift
integrates with the sl3
package (Coyle et al. 2020) to allow
for ensemble machine learning to be leveraged in the estimation
procedure.
For many practical applications (e.g., vaccine efficacy trials),
observed data is often subject to a two-phase sampling mechanism (i.e.,
through the use of a two-stage design). In such cases, efficient
estimators (of both varieties) must be augmented to construct unbiased
estimates of the population-level causal parameter. Rose and van der
Laan (2011) first introduced an augmentation procedure that relies on
introducing inverse probability of censoring (IPC) weights directly to
an appropriate loss function or to the efficient influence function
estimating equation. txshift
extends this approach to compute
IPC-weighted one-step and TML estimators of the counterfactual mean
outcome under a shift stochastic treatment regime. The package is
designed to implement the statistical methodology described in Hejazi et
al. (2020).
Install the most recent stable release from GitHub via
remotes
:
remotes::install_github("nhejazi/txshift", build_vignettes = FALSE)
To illustrate how txshift
may be used to ascertain the effect of a
treatment, consider the following example:
library(txshift)
library(haldensify)
set.seed(429153)
# simulate simple data
n_obs <- 1000
W <- replicate(2, rbinom(n_obs, 1, 0.5))
A <- rnorm(n_obs, mean = 2 * W, sd = 1)
Y <- rbinom(n_obs, 1, plogis(A + W + rnorm(n_obs, mean = 0, sd = 1)))
# now, let's introduce a a two-stage sampling process
C <- rbinom(n_obs, 1, plogis(W + Y))
# fit the full-data TMLE (ignoring two-phase sampling)
tmle <- txshift(W = W, A = A, Y = Y, delta = 0.5,
estimator = "tmle",
g_fit_args = list(fit_type = "hal",
n_bins = 5,
grid_type = "equal_mass",
lambda_seq = exp(seq(-1, -9, length = 300))),
Q_fit_args = list(fit_type = "glm",
glm_formula = "Y ~ .")
)
summary(tmle)
#> lwr_ci param_est upr_ci param_var eif_mean estimator n_iter
#> 0.7474 0.7782 0.8061 2e-04 7.0199e-11 tmle 0
# fit a full-data one-step estimator for comparison (again, no sampling)
os <- txshift(W = W, A = A, Y = Y, delta = 0.5,
estimator = "onestep",
g_fit_args = list(fit_type = "hal",
n_bins = 5,
grid_type = "equal_mass",
lambda_seq = exp(seq(-1, -9, length = 300))),
Q_fit_args = list(fit_type = "glm",
glm_formula = "Y ~ .")
)
summary(os)
#> lwr_ci param_est upr_ci param_var eif_mean estimator
#> 0.7472 0.7779 0.8059 2e-04 -1.6704e-03 onestep
#> n_iter
#> 0
# fit an IPCW-TMLE to account for the two-phase sampling process
ipcw_tmle <- txshift(W = W, A = A, Y = Y, delta = 0.5,
C = C, V = c("W", "Y"),
estimator = "tmle",
max_iter = 5,
ipcw_fit_args = list(fit_type = "glm"),
g_fit_args = list(fit_type = "hal",
n_bins = 5,
grid_type = "equal_mass",
lambda_seq =
exp(seq(-1, -9, length = 300))),
Q_fit_args = list(fit_type = "glm",
glm_formula = "Y ~ ."),
eif_reg_type = "glm"
)
summary(ipcw_tmle)
#> lwr_ci param_est upr_ci param_var eif_mean estimator
#> 0.7435 0.7765 0.8063 3e-04 -4.0365e-05 tmle
#> n_iter
#> 1
# compare with an IPCW-agumented one-step estimator under two-phase sampling
ipcw_os <- txshift(W = W, A = A, Y = Y, delta = 0.5,
C = C, V = c("W", "Y"),
estimator = "onestep",
ipcw_fit_args = list(fit_type = "glm"),
g_fit_args = list(fit_type = "hal",
n_bins = 5,
grid_type = "equal_mass",
lambda_seq =
exp(seq(-1, -9, length = 300))),
Q_fit_args = list(fit_type = "glm",
glm_formula = "Y ~ ."),
eif_reg_type = "glm"
)
summary(ipcw_os)
#> lwr_ci param_est upr_ci param_var eif_mean estimator
#> 0.7427 0.7758 0.8058 3e-04 -2.0555e-03 onestep
#> n_iter
#> 0
If you encounter any bugs or have any specific feature requests, please file an issue. Further details on filing issues are provided in our contribution guidelines.
Contributions are very welcome. Interested contributors should consult our contribution guidelines prior to submitting a pull request.
After using the txshift
R package, please cite the following:
@article{hejazi2020efficient-biom,
author = {Hejazi, Nima S and {van der Laan}, Mark J and Janes, Holly
E and Gilbert, Peter B and Benkeser, David C},
title = {Efficient nonparametric inference on the effects of
stochastic interventions under two-phase sampling, with
applications to vaccine efficacy trials},
year = {2020},
url = {http://arxiv.org/abs/2003.13771},
journal = {Biometrics (Methodology)},
publisher = {Wiley Online Library}
}
@article{hejazi2020txshift-joss,
author = {Hejazi, Nima S and Benkeser, David C},
title = {{txshift}: Efficient estimation of the causal effects of
stochastic interventions in {R}},
year = {2020},
journal = {under review at Journal of Open Source Software},
publisher = {The Open Journal}
}
@software{hejazi2020txshift-rpkg,
author = {Hejazi, Nima S and Benkeser, David C},
title = {{txshift}: Efficient Estimation of the Causal Effects of
Stochastic Interventions},
year = {2020},
url = {https://github.com/nhejazi/txshift},
note = {R package version 0.3.4}
}
R/tmle3shift
- An R
package providing an independent implementation of the same core
routines for the TML estimation procedure and statistical
methodology as is made available here, through reliance on a unified
interface for Targeted Learning provided by the
tmle3
engine of the tlverse
ecosystem.
R/medshift
- An R package
providing facilities to estimate the causal effect of stochastic
treatment regimes in the mediation setting, including classical
(IPW) and augmented double robust (one-step) estimators. This is an
implementation of the methodology explored by Dı́az and Hejazi
(2020).
R/haldensify
- A minimal
package for estimating the conditional density treatment mechanism
component of this parameter based on using the highly adaptive
lasso (Coyle, Hejazi, and van
der Laan 2020) in combination with a pooled hazard regression. This
package implements the methodology proposed by Dı́az and van der
Laan (2011).
The development of this software was supported in part through a grant from the National Institutes of Health: T32 LM012417-02.
© 2017-2020 Nima S. Hejazi
The contents of this repository are distributed under the MIT license. See below for details:
MIT License
Copyright (c) 2017-2020 Nima S. Hejazi
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of this software and associated documentation files (the "Software"), to deal
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