The Dataset
The dataset we will use here is Penrose et al. (1985). This dataset contains 252 observations and 19 variables, and is described below. First we need to load the data.
> fat <- read.table("fatdata.txt",header=TRUE, sep="\t")
> str(fat)
Table 1. Description of Percent Body Fat data
|
Variable |
Description |
|---|---|
|
id |
Case Number |
|
pctfat.brozek |
Percent body fat using Brozek's equation, 457/Density - 414.2 |
|
pctfat.siri |
Percent body fat using Siri's equation, 495/Density - 450 |
|
density |
Density (gm/cm^3) |
|
age |
Age (yrs) |
|
weight |
Weight (lbs) |
|
height |
Height (inches) |
|
adiposity |
Adiposity index = Weight/Height^2 (kg/m^2) |
|
fatfreeweight |
Fat Free Weight = (1 - fraction of body fat) * Weight, using Brozek's formula (lbs) |
|
neck |
Neck circumference (cm) |
|
chest |
Chest circumference (cm) |
|
abdomen |
Abdomen circumference (cm) "at the umbilicus and level with the iliac crest" |
|
hip |
Hip circumference (cm) |
|
thigh |
Thigh circumference (cm) |
|
knee |
Knee circumference (cm) |
|
ankle |
Ankle circumference (cm) |
|
biceps |
Extended biceps circumference (cm) |
|
forearm |
Forearm circumference (cm) |
|
wrist |
Wrist circumference (cm) "distal to the styloid processes" |
The percentage of body fat is a measure to assess a person's health and is measured through an underwater weighing technique. In this lecture we will try to build a formula to predict an individual's body fat, based on variables in the dataset.
