Isolate a geom layer from a plot

get_geom_layer returns a geom layer from a plot along with the global data sets and aesthetic mappings that the layer may inherit from.

Usage

get_geom_layer(p, geom = NULL, i = NULL)

Arguments

p

A ggplot object

geom

A character string found in the suffix of a ggplot2 geom function, e.g. "point".

i

A numerical index, e.g. 1.

Value

An object with class layer_to_check to be manipulated further with ggcheck functions.

Details

Users can specify a layer in one of 3 ways:

1. By order of appearance with i. The first layer to appear in the plot (the one drawn first, on the bottom) corresponds to i = 1.

2. By type of geom with geom. get_geom_layer will return the first layer that uses the geom.

3. By a combination of geom and i. get_geom_layer will return the ith layer that uses the geom.

Examples

require(ggplot2)
p <- ggplot(data = mpg, mapping = aes(x = displ, y = hwy)) +
  geom_point(color = "red") +
  geom_point(mapping = aes(color = class)) +
  geom_smooth(se = FALSE)

get_geom_layer(p, i = 1)
#> $layer
#> geom_point: na.rm = FALSE
#> stat_identity: na.rm = FALSE
#> position_identity 
#> 
#> $global_data
#> # A tibble: 234 × 11
#>    manufacturer model      displ  year   cyl trans drv     cty   hwy fl   
#>    <chr>        <chr>      <dbl> <int> <int> <chr> <chr> <int> <int> <chr>
#>  1 audi         a4           1.8  1999     4 auto… f        18    29 p    
#>  2 audi         a4           1.8  1999     4 manu… f        21    29 p    
#>  3 audi         a4           2    2008     4 manu… f        20    31 p    
#>  4 audi         a4           2    2008     4 auto… f        21    30 p    
#>  5 audi         a4           2.8  1999     6 auto… f        16    26 p    
#>  6 audi         a4           2.8  1999     6 manu… f        18    26 p    
#>  7 audi         a4           3.1  2008     6 auto… f        18    27 p    
#>  8 audi         a4 quattro   1.8  1999     4 manu… 4        18    26 p    
#>  9 audi         a4 quattro   1.8  1999     4 auto… 4        16    25 p    
#> 10 audi         a4 quattro   2    2008     4 manu… 4        20    28 p    
#> # … with 224 more rows, and 1 more variable: class <chr>
#> 
#> $global_mapping
#> Aesthetic mapping: 
#> * `x` -> `displ`
#> * `y` -> `hwy`
#> 
#> attr(,"class")
#> [1] "layer_to_check"
get_geom_layer(p, geom = "smooth")
#> $layer
#> geom_smooth: na.rm = FALSE, orientation = NA, se = FALSE
#> stat_smooth: na.rm = FALSE, orientation = NA, se = FALSE
#> position_identity 
#> 
#> $global_data
#> # A tibble: 234 × 11
#>    manufacturer model      displ  year   cyl trans drv     cty   hwy fl   
#>    <chr>        <chr>      <dbl> <int> <int> <chr> <chr> <int> <int> <chr>
#>  1 audi         a4           1.8  1999     4 auto… f        18    29 p    
#>  2 audi         a4           1.8  1999     4 manu… f        21    29 p    
#>  3 audi         a4           2    2008     4 manu… f        20    31 p    
#>  4 audi         a4           2    2008     4 auto… f        21    30 p    
#>  5 audi         a4           2.8  1999     6 auto… f        16    26 p    
#>  6 audi         a4           2.8  1999     6 manu… f        18    26 p    
#>  7 audi         a4           3.1  2008     6 auto… f        18    27 p    
#>  8 audi         a4 quattro   1.8  1999     4 manu… 4        18    26 p    
#>  9 audi         a4 quattro   1.8  1999     4 auto… 4        16    25 p    
#> 10 audi         a4 quattro   2    2008     4 manu… 4        20    28 p    
#> # … with 224 more rows, and 1 more variable: class <chr>
#> 
#> $global_mapping
#> Aesthetic mapping: 
#> * `x` -> `displ`
#> * `y` -> `hwy`
#> 
#> attr(,"class")
#> [1] "layer_to_check"
get_geom_layer(p, geom = "point", i = 2)
#> $layer
#> mapping: colour = ~class 
#> geom_point: na.rm = FALSE
#> stat_identity: na.rm = FALSE
#> position_identity 
#> 
#> $global_data
#> # A tibble: 234 × 11
#>    manufacturer model      displ  year   cyl trans drv     cty   hwy fl   
#>    <chr>        <chr>      <dbl> <int> <int> <chr> <chr> <int> <int> <chr>
#>  1 audi         a4           1.8  1999     4 auto… f        18    29 p    
#>  2 audi         a4           1.8  1999     4 manu… f        21    29 p    
#>  3 audi         a4           2    2008     4 manu… f        20    31 p    
#>  4 audi         a4           2    2008     4 auto… f        21    30 p    
#>  5 audi         a4           2.8  1999     6 auto… f        16    26 p    
#>  6 audi         a4           2.8  1999     6 manu… f        18    26 p    
#>  7 audi         a4           3.1  2008     6 auto… f        18    27 p    
#>  8 audi         a4 quattro   1.8  1999     4 manu… 4        18    26 p    
#>  9 audi         a4 quattro   1.8  1999     4 auto… 4        16    25 p    
#> 10 audi         a4 quattro   2    2008     4 manu… 4        20    28 p    
#> # … with 224 more rows, and 1 more variable: class <chr>
#> 
#> $global_mapping
#> Aesthetic mapping: 
#> * `x` -> `displ`
#> * `y` -> `hwy`
#> 
#> attr(,"class")
#> [1] "layer_to_check"