Writing Function for calculating and classifying BMI in R-Markdown

1. Introduction

Body Mass Index is a simple calculation using a person’s height and weight. The formula is BMI = kg/m2 where kg is a person’s weight in kilograms and m2 is their height in metres squared.

2.1 Formula calculating BMI.

Formula for converting BMI.

\[ BMI = \frac{Weight}{Height^2} \] For example we want to calculate BMI for a person with weight = 68 kg and height = 1.62 m. \[ BMI = \frac{68}{1.62^2} \]

bmi <- round(68/1.62^2, digits = 1)

With this above, BMI is calculated 25.9

2.2 Function calculating BMI.

bmi_cal <- function(height, weight){
bmi <- round(height/weight^2, digits = 1)
return(bmi)
}

Example a persion with weight = 68 and height = 1.62 We can calculate and asign the name bmi as `bmi <- round(68/1.62^2, digits = 1)

bmi <- bmi_cal(68, 1.62)
print(bmi)

## [1] 25.9

`

Hence, weight = 68 and height = 1.62to function and we can culate BMIof this persion is 25.9

3.1 Formula for classifying of BMI.

We define BMI catogories as following.

• BMI < 18.5 is underweight.
• BMI ranges from 18.5 -> 24.99 is normal.
• BMI ranges from 23 -> 24.99 is overweight.
• BMI > 25 is obese.

3.2 Function classifying BMI

R function.

bmi_categories<- function(bm){
  b_m_i <- (ifelse(bm < 18.5, "Underweight",(ifelse (18.5<= bm & bm  <25 ,  "Normal Weight",(ifelse (25<= bm & bm <30, "Overweight",(ifelse (30<= bm, "Obese",""))))))))
  return(b_m_i)
}

We calculate using this function bmi_categories(bmi)

bmi_categories(bmi)

## [1] "Overweight"

Conclustion: This persion with weight = 68 and height = 1.62. BMI of this one is 25.9 and can be classified as Overweight