Each of the following linear combinations creates a new variable ci. For each equation listed below, create one time series plot similar to Figure 10.3 that includes the standardized Dow, S&P, and NASDAQ closing values (z1, z2, z3) and ci. Then explain what characteristic of the data is emphasized by that linear combination.
a. c1 = 1z1 + 0z2 + 0z3
b. c2 = 1z1 – 1z2 + 0z3
c. c3 = 1/3 z1 + 1/3 z2 + 1/3 3
d. c4 = 0z1 + 0z2 – 1z3