Low-Back-Merger Shift Index

A function to quickly calculate the Low-Back-Merger Shift Index, per Becker (2019).

lbms_index(df, vowel_col, F1_col, F2_col, beet, bit, bet, bat)

Arguments

df

The dataframe containing the formant measurements you want to base the calculation off of.

vowel_col

The name of the column containing the name of the vowel (e.g. vowel)

F1_col

The name of the column containing the F1 measurements (e.g. F1_norm)

F2_col

The name of the column containing the F2 measurements (e.g. F2_norm)

beet

A string that indicates which vowels belong to the BEET class of words (e.g. "IY")

bit

A string that indicates which vowels belong to the BIT class of words (e.g. "IH")

bet

A string that indicates which vowels belong to the BET class of words (e.g. "EH")

bat

A string that indicates which vowels belong to the BAT class of words (e.g. "AE")

Value

A summarized dataframe with the LBMS Index.

Details

If you would like to calculate the LBMS Index for each speaker, be sure to the data beforehand with group_by() (see the examples). Also, per Becker's (2019) recommendation, it is recommended that you exclude tokens before nasals, laterals, rhotics, and /g/ before the calculation. It is also recommended to run the function on Lobanov-normalized data.

Note that this is a new function and has not been tested robustly yet.

References

Becker, Kara, ed. The Low-Back-Merger Shift: Uniting the Canadian Vowel Shift, the California Vowel Shift, and Short Front Vowel Shifts across North America. Publication of the American Dialect Society 104. Durham, NC: Duke University Press, 2019.

Examples

suppressPackageStartupMessages(library(tidyverse))
# This dataset has following segment and normalized data already
darla <- joeysvowels::darla
darla %>%
  filter(!fol_seg %in% c("L", "R", "M", "N", "NG", "G")) %>%
  lbms_index(vowel, F1_LobanovNormed_unscaled, F2_LobanovNormed_unscaled, "IY", "IH", "EH", "AE")
#> # A tibble: 1 × 1
#> # Rowwise: 
#>   lbms_index
#>        <dbl>
#> 1       1.50

# This dataset has multiple speakers and needs to be normalized
idahoans <- joeysvowels::idahoans
idahoans %>%
  group_by(speaker) %>%
  mutate(F1_lob = scale(F1),
         F2_lob = scale(F2)) %>%
  lbms_index(vowel, F1_lob, F2_lob, "IY", "IH", "EH", "AE")
#> # A tibble: 10 × 2
#> # Rowwise:  speaker
#>    speaker lbms_index
#>    <fct>        <dbl>
#>  1 01            2.33
#>  2 02            1.92
#>  3 03            1.85
#>  4 04            2.04
#>  5 05            2.05
#>  6 06            1.64
#>  7 07            2.17
#>  8 08            2.21
#>  9 09            2.07
#> 10 10            2.00