tidystats

The goal of tidystats is to provide a "tidy-in, tidy-out" interface to statistical tests, including implementations for many tests in the stats package. Generally, a test object will get created using columns from a (tidy) data.frame. For example, a t-test using the sleep dataset would look like this:

head(sleep)
#>   extra group ID
#> 1   0.7     1  1
#> 2  -1.6     1  2
#> 3  -0.2     1  3
#> 4  -1.2     1  4
#> 5  -0.1     1  5
#> 6   3.4     1  6
test <- tidy_t_test(sleep, values = extra, groups = group)

Installation

You can install tidystats from github with:

# install.packages("devtools")
devtools::install_github("paleolimbot/tidystats")

Philosophy

The (currently loose) philosphy of this package is to make statistics easier to teach by using consistent terminology and syntax across functions. So far, the loose set of rules is as follows:

• Functions should be prefixed with tidy_, unless somebody can think of something better.

• All functions and argument names should use tidy_style.

• Statistical tests should be created with .data (a data.frame) as an optional first argument. If .data is provided, arguments that create the data for the test should be evaluated using dplyr::transmute(). If not, they should be evaluated using tibble::tibble(). This lets quick one-off calls that let the user skip creating the initial data.frame. This is currently implemented in data_eval(). Some statistical tests are probably better suited to the dplyr::select() syntax (e.g., PCA), where the everything() or starts_with() selectors might be useful. This could be implemented using something like the dplyr::vars() wrapper, but isn't yet. Tidy evaluation is a must!

• The output of a test function (like tidy_t_test()) should be an S3 classed list. The current approach is to return the same object that the stats equivalent would return with classes tacked on to the front, meaning it can be used like the stats class.

• A print() method (preferably using pretty cli and crayon output), a broom::tidy() method (multi-row summary of the result), a broom::glance() method (one-row summary of fit quality), a ggplot2::autoplot() method should be implemented for the test class.

• If the concept of applying the model to a new dataset is relevant (predicting), predict.s3_class_name() should be implemented in the following way:

  • The first argument is the model (it has to be this way for S3 dispatch to work...another function called something like tidy_predict() could put the .data first to work slightly better with the pipe).

  • The (optional) .data argument and ... are evaluated using data_eval() to create what is usually called newdata in the stats implementation.

  • The output should be a tibble with the same number of rows as the input .data. If .data is given (there was an input data frame from which variables were taken), the input variables should not be included in the output. If .data was not given (i.e., the use created the data from within ...), the input variables should be included in the output. This facilitates quick one-off predicting for interactive use, and df %>% bind_cols(., predict(test, .)) for adding predicted data to an existing data frame.

• Probably more rules to come as more writing is done...

Contributing

Please contribute to this package! I imagine there are a lot of ideas of how to go about this, and now is a great time to try all of them.