# Dealing with R data frames Data frames are a central concept in R. A data frame is a 2-dimensional matrix with optional column and row names. The data is (normally) column-oriented. This differs from the row-oriented view on data in Prolog, for example as a set of solutions for a predicate. The library(r_data) provides predicates for creating and accessing R data frames. ## Creating a data frame from solutions Below we define a relation sin/3 based on the sine function and turn the resulting solutions into a data frame called `df`. The subsequent examples plot the relation using _ggplot2_ and provide some timing for exchanging large datasets.

% Y is sin(X) for X in 0..Max sin(Max, X, Y) :- between(0, Max, X), Y is sin(X*pi/180).

r_data_frame(df, [x=X,y=Y], sin(10, X, Y)), <- df.

time(r_data_frame(df, [x=X,y=Y], sin(360, X, Y))), time(<- library("ggplot2")), time(<- ggplot(data=df, aes(x=x, y=y)) + geom_line()).

time(r_data_frame(df, [x=X,y=Y], sin(1 000 000, X, Y))).

time(r_data_frame(df, [x=X,y=Y], sin(1 000 000, X, Y))), time(r_data_frame_to_dicts(df, _Dicts)).

## Importing data frames to Prolog The predicates r_data_frame_to_dicts/2 and r_data_frame_to_rows/3 translate the column-oriented data frame to a list of row oriented dicts or terms. We use the example on the predefined R `mtcars` data frame.

:- use_rendering(table).

r_data_frame_to_dicts(mtcars, Dicts).

r_data_frame_rownames(mtcars, Rows).

## Documentation Below is the reference documentation for the predicates in library(r_data). - [[r_data_frame/3]] - [[r_data_frame_from_rows/2]] - [[r_data_frame_to_dicts/2]] - [[r_data_frame_to_rows/3]] - [[r_data_frame_colnames/2]] - [[r_data_frame_rownames/2]]