Stretch correlation data frame into long format.

Source: R/reshape.R

stretch is a specified implementation of tidyr::gather() to be applied to a correlation data frame. It will gather the columns into a long-format data frame. The term column is handled automatically.

stretch(x, na.rm = FALSE, remove.dups = FALSE)

Arguments

x

cor_df. See correlate.
na.rm

Boolean. Whether rows with an NA correlation (originally the matrix diagonal) should be dropped? Will automatically be set to TRUE if mirror is FALSE.
remove.dups

Removes duplicate entries, without removing all NAs

Value

tbl with three columns (x and y variables, and their correlation)

Examples

x <- correlate(mtcars)

#> 
#> Correlation method: 'pearson'
#> Missing treated using: 'pairwise.complete.obs'
stretch(x)  # Convert all to long format

#> # A tibble: 121 x 3
#>    x     y          r
#>    <chr> <chr>  <dbl>
#>  1 mpg   mpg   NA    
#>  2 mpg   cyl   -0.852
#>  3 mpg   disp  -0.848
#>  4 mpg   hp    -0.776
#>  5 mpg   drat   0.681
#>  6 mpg   wt    -0.868
#>  7 mpg   qsec   0.419
#>  8 mpg   vs     0.664
#>  9 mpg   am     0.600
#> 10 mpg   gear   0.480
#> # … with 111 more rows
stretch(x, na.rm = FALSE)  # omit NAs (diagonal in this case)

#> # A tibble: 121 x 3
#>    x     y          r
#>    <chr> <chr>  <dbl>
#>  1 mpg   mpg   NA    
#>  2 mpg   cyl   -0.852
#>  3 mpg   disp  -0.848
#>  4 mpg   hp    -0.776
#>  5 mpg   drat   0.681
#>  6 mpg   wt    -0.868
#>  7 mpg   qsec   0.419
#>  8 mpg   vs     0.664
#>  9 mpg   am     0.600
#> 10 mpg   gear   0.480
#> # … with 111 more rows

x <- shave(x)  # use shave to set upper triangle to NA and then...
stretch(x, na.rm = FALSE)  # omit all NAs, therefore keeping each

#> # A tibble: 121 x 3
#>    x     y          r
#>    <chr> <chr>  <dbl>
#>  1 mpg   mpg   NA    
#>  2 mpg   cyl   -0.852
#>  3 mpg   disp  -0.848
#>  4 mpg   hp    -0.776
#>  5 mpg   drat   0.681
#>  6 mpg   wt    -0.868
#>  7 mpg   qsec   0.419
#>  8 mpg   vs     0.664
#>  9 mpg   am     0.600
#> 10 mpg   gear   0.480
#> # … with 111 more rows
                             # correlation only once.