The Art of R Programming

To explain whatmapsound()does, let’s devise some terminology, illus-

trated by thex→hexample earlier. We’ll callxthesource value, withh,s,

and so on being themapped values.

Here are the formal parameters:

• df: A data frame consisting of the pronunciation data of two fangyan


• fromcolandtocol: Names indfof the source and mapped columns


• sourceval: The source value to be mapped, such asxin the preceding
  example

Here is the head of a typical two-fangyan data frame,canman8, that would

be used fordf:

> head(canman8)

Ch char Can Man Can cons Can sound Can tone Man cons Man sound Man tone

1 一 yat1 yi1 y at 1 y i 1

2 丁 ding1 ding1 d ing 1 d ing 1

3 七 chat1 qi1 ch at 1 q i 1

4 丈jeung6 zhang4 j eung 6 zh ang 4

5 上seung5 shang3 s eung 5 sh ang 3

6 下 ha5 xia4 h a5xia4

The function returns a list consisting of two components:

• counts: A vector of integers, indexed by the mapped values, showing the
  counts of those values. The elements of the vector are named according
  to the mapped values.


• images: A list of character vectors. Again, the indices of the list are the
  mapped values, and each vector consists of all the characters that corre-
  spond to the given mapped value.

To make this concrete, let’s try it out:

> m2cx <- mapsound(canman8,"Man cons","Can cons","x")

> m2cx$counts

chfghjkkwnsy

152187124218121

We see thatxmaps toch15 times, tof2 times, and so on. Note that we

could have calledsort()tom2cx$countsto view the mapped images in order,

from most to least frequent.

The Mandarin-speaking learner of Cantonese can then see that if he

wishes to know the Cantonese pronunciation of a word whose Mandarin

romanized form begins withx, the Cantonese almost certainly begins with

hors. Little aids like this should help the learning process quite a bit.

To try to discern more patterns, the learner may wish to determine in

which charactersxmaps toch, for example. We know from the result of the

preceding example that there are six such characters. Which ones are they?

116 Chapter 5