# Examples of grid corrgrams

## Package overview

The `corrgram` package provides functions for creating corrgrams using three different graphics systems, base, grid, and lattice.

Base R graphics + single function `corrgram()` for dataframes or matrices. + Enables most features found in the paper by @friendly2002corrgrams. - No automatic legend. - Not easily combined with other graphics.

`lattice` graphics + Separate panel functions for `lattice::levelplot()` for dataframes and `lattice::splom()` for correlation matrices. + Enables automatic legend. + Enables corrgrams conditioned on other variables. + Can be combined with other lattice graphics for complex figures. - Not feature complete compared to base R.

`grid` graphics + single function `corrgram2()` for either dataframes or correlation matrices. + Enables automatic legend. + Can be combined with other grid graphics for complex figures. - Not feature complete compared to base R. + Faster than base R when evaluated inside Positron.

## This vignette

This vignette demonstrates how to create corrgrams using `grid` graphics with the `corrgram2()` function and a variety of panel functions for visualizing correlations in different ways.

## Grid Panels for corrgram2

This vignette demonstrates the use of grid-based panels in `corrgram2`, which provide flexible and modern correlation matrix visualizations.

## Correlation matrix corrgram in grid

The `vote` dataset contains roll call voting records for US Senators. Here we show a grid-based correlation plot with absolute correlations, ordering, and a legend.

    corrgram2(vote, abs = TRUE, order = TRUE, legend = TRUE, title = "vote data")

## Dataframe corrgram in grid

The `auto` dataset contains various automobile attributes. We select a subset of numeric variables and display a grid-based correlation plot using the fill panel.

    vars6 <- setdiff(colnames(auto), c("Model", "Origin"))
    corrgram2(auto[, vars6],
              lower.panel = grid_panel.shade, upper.panel=grid_panel.pie,
              title = "auto data", legend = TRUE)