Re-fit a model with standardized dataSource:
Performs a standardization of data (z-scoring) using
standardize() and then re-fits the model to the standardized data.
Standardization is done by completely refitting the model on the standardized data. Hence, this approach is equal to standardizing the variables before fitting the model and will return a new model object. This method is particularly recommended for complex models that include interactions or transformations (e.g., polynomial or spline terms). The
robust (default to
FALSE) argument enables a robust standardization of data, based on the
median and the
MAD instead of the
mean and the
# S3 method for default standardize( x, robust = FALSE, two_sd = FALSE, weights = TRUE, verbose = TRUE, include_response = TRUE, ... )
A statistical model.
TRUE, centering is done by subtracting the median from the variables and dividing it by the median absolute deviation (MAD). If
FALSE, variables are standardized by subtracting the mean and dividing it by the standard deviation (SD).
TRUE, the variables are scaled by two times the deviation (SD or MAD depending on
robust). This method can be useful to obtain model coefficients of continuous parameters comparable to coefficients related to binary predictors, when applied to the predictors (not the outcome) (Gelman, 2008).
TRUE(default), a weighted-standardization is carried out.
Toggle warnings and messages on or off.
TRUE(default), the response value will also be standardized. If
FALSE, only the predictors will be standardized.
Note that for GLMs and models with non-linear link functions, the response value will not be standardized, to make re-fitting the model work.
If the model contains an
stats::offset(), the offset variable(s) will be standardized only if the response is standardized. If
two_sd = TRUE, offsets are standardized by one-sd (similar to the response).
include_responserefers to the outcome in the y model; m model's response will always be standardized when possible).
Arguments passed to or from other methods.
Standardization for generalized linear models (GLM, GLMM, etc) is done only with respect to the predictors (while the outcome remains as-is, unstandardized) - maintaining the interpretability of the coefficients (e.g., in a binomial model: the exponent of the standardized parameter is the OR of a change of 1 SD in the predictor, etc.)
standardize_parameters(model, method = "refit") do
not standardize categorical predictors (i.e. factors) / their
dummy-variables, which may be a different behaviour compared to other R
packages (such as lm.beta) or other software packages (like SPSS). To
mimic such behaviours, either use
standardize_parameters(model, method = "basic") to obtain post-hoc standardized parameters, or standardize the data
standardize(data, force = TRUE) before fitting the
When the model's formula contains transformations (e.g.
y ~ exp(X)) the
transformation effectively takes place after standardization (e.g.,
exp(scale(X))). Since some transformations are undefined for none positive
values, such as
sqrt(), the relevel variables are shifted (post
Z - min(Z) + 1 or
Z - min(Z) (respectively).