Classify a Chao tone numeral string as a shape

Returns a short human-readable shape name (e.g., "level", "rising", "falling", "dipping", "peaking", or one of the finer-grained "low level" / "mid level" / "high level" labels for repeated-digit strings). Used by contour_to_chao() to add a shape column to its output, but also exposed as a standalone utility for classifying numerals from external sources.

Usage

classify_contour(chao_str)

Arguments

chao_str

A character string of Chao digits, e.g. "55", "214", "35".

Value

A character string naming the shape.

Details

Classification rules:

• All digits identical: one of "low level", "mid-low level", "mid level", "mid-high level", "high level" according to the digit value.

• Three or more digits with an interior minimum below both endpoints: "dipping".

• Three or more digits with an interior maximum above both endpoints: "peaking".

• Otherwise, "rising" if the last digit is higher than the first, "falling" if lower, "level" if equal.

References

Chao, Y. R. (1930). A system of tone-letters. Le Maître Phonétique, 30, 24–27.

Xu, C., & Zhang, C. (2024). A cross-linguistic review of citation tone production studies: Methodology and recommendations. The Journal of the Acoustical Society of America, 156(4), 2538–2565. doi:10.1121/10.0032356

See also

contour_to_chao() which calls this internally to populate the shape column.

Examples

classify_contour("55")    # "high level"
#> [1] "high level"
classify_contour("214")   # "dipping"
#> [1] "dipping"
classify_contour("35")    # "rising"
#> [1] "rising"
classify_contour("51")    # "falling"
#> [1] "falling"