symbolize converts numeric vectors to symbolic vectors. It is a helper
function for muti.
symbolize(xy)
| xy | An n x 2 |
|---|
An (n-2) x 2 matrix of integer symbols that indicate whether
the i-th value, based on the i-1 and i+1 values, is a "trough" (=1),
"decrease" (=2), "same" (=3), "increase" (=4), or "peak" (=5).