```{r chunk_options, echo=FALSE}
knitr::opts_chunk$set(echo=FALSE, warning=FALSE, message=FALSE)
```

## Preliminaries

I first need to load the dplyr and ggplot libraries.

```{r load_libraries, message=FALSE, echo=FALSE}
library(dplyr)
library(ggplot2)
```

I will then load the original "portal data" file.

```{r load_data}
surveys <- read.csv("http://kbroman.org/datacarp/portal_data_joined.csv")
```

These data have `r nrow(surveys)` rows and `r ncol(surveys)` columns.

Here's a scatterplot of hindfoot length versus weight:

```{r scatterplot_hfl_vs_weight, echo=FALSE, warning=FALSE}
ggplot(surveys, aes(x=weight, y=hindfoot_length)) +
    geom_point()
```