Delta F Normalize

Usage

norm_deltaF(
  .data,
  ...,
  .by = NULL,
  .by_formant = FALSE,
  .drop_orig = FALSE,
  .keep_params = FALSE,
  .names = "{.formant}_df",
  .silent = FALSE
)

Arguments

.data: A data frame containing vowel formant data
...: <tidy-select> One or more unquoted expressions separated by commas. These should target the vowel formant data columns.
.by: <tidy-select> A selection of columns to group by. Typically a column of speaker IDs.
.by_formant: Ignored by this procedure
.drop_orig: Whether or not to drop the original formant data columns.
.keep_params: Whether or not to keep the Location (*_.L) and Scale (*_.S) normalization parameters
.names: A glue::glue() expression for naming the normalized data columns. The "{.formant}" portion corresponds to the name of the original formant columns.
.silent: Whether or not the informational message should be printed.

Value

A data frame of Delta F normalized formant values.

Details

$$ \hat{F}_{ij} = \frac{F_{ij}}{S} $$ $$ S = \frac{1}{MN}\sum_{i=1}^M\sum_{j=1}^N \frac{F_{ij}}{i-0.5} $$

Where

$\hat{F}$ is the normalized formant
$i$ is the formant number
$j$ is the token number

References

Johnson, K. (2020). The ΔF method of vocal tract length normalization for vowels. Laboratory Phonology: Journal of the Association for Laboratory Phonology, 11(1), Article 1. https://doi.org/10.5334/labphon.196

Examples

library(tidynorm)
ggplot2_inst <- require(ggplot2)

speaker_data_deltaF <- speaker_data |>
  norm_deltaF(
    F1:F3,
    .by = speaker,
    .names = "{.formant}_df"
  )
#> Normalization info
#> • normalized `F1`, `F2`, and `F3`
#> • normalized values in `F1_df`, `F2_df`, and `F3_df`
#> • grouped by `speaker`
#> • formant extrinsic
#> 

## this is equivalent to
# speaker_data |>
#   norm_generic(
#     F1:F3,
#     .by = speaker,
#     .S = mean(.formant/(.formant_num - 0.5), na.rm = T)
#   )

if(ggplot2_inst){
  ggplot(
    speaker_data_deltaF,
    aes(
      F2_df,
      F1_df,
      color = speaker
    )
  )+
    stat_density_2d(
      bins = 4
    )+
    scale_color_brewer(
      palette = "Dark2"
    )+
    scale_x_reverse()+
    scale_y_reverse()+
    coord_fixed()
}