---
title: "Scrape Michigan Lakes"
author: "Jemma Stachelek"
date: "`r Sys.Date()`"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Scrape Michigan Lakes}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r }
library(wikilake)
```

## Generate list of Michigan Lakes

### Get Wikipedia URL of Category
```{r category url, eval = FALSE}
res <- WikipediR::page_info("en", "wikipedia",
  page = "Category:Lakes of Michigan")
```

### Scrape lake names
```{r scrape names, eval = FALSE}
res <- xml2::read_html(res$query$pages[[1]]$canonicalurl)
res <- rvest::html_nodes(res, "#mw-pages .mw-category")
res <- rvest::html_nodes(res, "li")
res <- rvest::html_nodes(res, "a")
res <- rvest::html_attr(res, "title")
```

### Remove junk names
```{r remove junk names, eval = FALSE}
res <- res[!(seq_len(length(res)) %in% grep("List", res))]
res <- res[!(seq_len(length(res)) %in% grep("Watershed", res))]
res <- res[!(seq_len(length(res)) %in% grep("lakes", res))]
res <- res[!(seq_len(length(res)) %in% grep("Mud Lake", res))]
```

### Scrape tables
```{r scrape tables, eval = FALSE}
res <- lapply(res, lake_wiki)

# remove missing coordinates
res <- res[unlist(lapply(res, function(x) !is.na(x[, "Lat"])))]
```

### Collapse list to `data.frame`

```{r collapse list to data.frame, eval = FALSE}
res_df_names <- unique(unlist(lapply(res, names)))
res_df <- data.frame(matrix(NA, nrow = length(res),
  ncol = length(res_df_names)))
names(res_df) <- res_df_names
for (i in seq_len(length(res))) {
  dt_pad <- data.frame(matrix(NA, nrow = 1,
    ncol = length(res_df_names) - ncol(res[[i]])))
  names(dt_pad) <- res_df_names[!(res_df_names %in% names(res[[i]]))]
  dt <- cbind(res[[i]], dt_pad)
  dt <- dt[, res_df_names]
  res_df[i, ] <- dt
}
```

```{r echo=FALSE, eval=FALSE}
good_cols <- data.frame(as.numeric(as.character(apply(res_df,
  2, function(x) sum(!is.na(x))))))
good_cols <- cbind(good_cols, names(res_df))
good_cols <- good_cols[good_cols[, 1] > 20, 2]
good_cols <- as.character(good_cols)

res_df <- res_df[, good_cols]
```

```{r echo = FALSE}
data(milakes)
res_df <- milakes
```

### Map lakes

```{r map lakes, fig.height=6,fig.align="center"}
library(sp)

coordinates(res_df) <- ~ Lon + Lat
map("state", region = "michigan", mar = c(0, 0, 0, 0))
points(res_df, col = "red", pch = 19)
```

```{r lake depth distribution }
hist(log(res_df$`Max. depth`), main = "", xlab = "Max depth (log(m))")
```
