Most R calculations begin with vectors. Knowing their type and length prevents silent coercion and indexing errors from spreading into later analysis.

Base R; no external data or packages.

indexed return: 100 × cumulative product(1 + r)

1. Step 1Define every variable and unit.
2. Step 2Check assumptions and information timing.
3. Step 3Calculate, verify, and interpret in context.

Variable

A numeric vector with one missing observation.

Model choice

Vectorized arithmetic applies the same rule element by element; recycling is safe only when intentional.

Calculation

Type = double; values above 4 are 4.4 and 5.2; available-case mean = 3.85.

Interpretation

The logical mask retains two high observations, while na.rm removes one unavailable value only for this calculation.

Reasonableness check

Removing NA does not explain why the value is missing or whether the available observations are representative.

The logical mask retains two high observations, while na.rm removes one unavailable value only for this calculation. Limitation: Removing NA does not explain why the value is missing or whether the available observations are representative.

Values above four are highlighted conceptually by taller bars.

Run the self-contained starter code in the protected STATLAB R runner. The code prints an auditable result and avoids network or unrestricted file access.

Compare your result with the definition, units, and model assumptions—not only with a target number.

Complete these without looking at the selected solutions. More than one defensible program may exist.

These are compact solution routes. Confirm dimensions, units, and any changed modelling choices.

Understand atomic vectors, coercion, vectorized operations, missing values, and safe subsetting.

Name the assumption, evidence you would seek, and how the recommendation might change.

Reach 70% to complete the chapter. Explanations appear after submission.