solution-exercise3.Rmd

---
title: "Exercise 3"
author: "Mark Dunning"
date: '`r format(Sys.time(), "Last modified: %d %b %Y")`'
output: pdf_document
---


# Reading the data

```{r}
patients <- read.delim("patient-info.txt")



```

# Analysis

```{r}
BMI <- (patients$Weight)/((patients$Height/100)^2)
upper.limit <- mean(BMI,na.rm = TRUE) + 2*sd(BMI,na.rm = TRUE)
```

# Plotting

```{r}
plot(BMI)
# Add a horizonal line:
abline(h=upper.limit) 
```

## Write out the results

```{r}
patients$BMI <- round(BMI,1)
candidates <- which(BMI > upper.limit)
write.csv(patients[candidates,], file="selectedSamples.csv")
```

# Exercise

```{r}
lower.limit <- mean(BMI,na.rm = TRUE) - 2*sd(BMI,na.rm = TRUE)
underweight.candidates <- which(BMI < lower.limit & patients$Smokes == "Smoker") 
```

```{r}
write.csv(patients[underweight.candidates,], "underweight_candidates.csv")
```