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Scrape Amazon's Trade-In Value
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| library(rvest) | |
| urls_df = read.csv("AmazonBookURLs.csv", stringsAsFactors = FALSE, comment.char = "") | |
| load(file = "AmazonBookPrices.RData") | |
| price_df_temp = data.frame(Title = urls_df$Title, | |
| Date = Sys.time(), | |
| Price = NA_real_, stringsAsFactors = FALSE) | |
| for (i in 1:nrow(urls_df)) { | |
| tradein_html = urls_df$URL[i] %>% html() %>% | |
| html_node("#tradeInButton_tradeInValue") | |
| if (is.null(tradein_html)) { | |
| next | |
| } | |
| price = tradein_html %>% | |
| html_text() %>% | |
| gsub("(^[[:space:]]+\\$|[[:space:]]+$)", "", .) %>% | |
| as.numeric() | |
| price_df_temp$Price[i] = price | |
| } | |
| price_df = rbind(price_df, price_df_temp) | |
| save(price_df, file = "AmazonBookPrices.RData") |
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| Title | URL | |
|---|---|---|
| Data Clustering C++ | http://www.amazon.com/Data-Clustering-Object-Oriented-Knowledge-Discovery/dp/1439862230 | |
| Transportation Statistics and Microsimulation | http://www.amazon.com/Transportation-Statistics-Microsimulation-Clifford-Spiegelman/dp/1439800235 | |
| Fundamentals of Transportation and Traffic Operations | http://www.amazon.com/Fundamentals-Transportation-Traffic-Operations-Daganzo/dp/0080427855 | |
| A First Course in Stochastic Processes | http://www.amazon.com/First-Course-Stochastic-Processes-Second/dp/0123985528 | |
| A Probability Path | http://www.amazon.com/A-Probability-Path-Sidney-Resnick/dp/081764055X | |
| A Primer on Linear Models | http://www.amazon.com/Primer-Linear-Chapman-Statistical-Science/dp/1420062018 | |
| Statistical Approach to Genetic Epidemiology | http://www.amazon.com/Statistical-Approach-Genetic-Epidemiology-Applications/dp/3527323899 | |
| Intro Trans Engineering | http://www.amazon.com/Introduction-Transportation-Engineering-Banks-James/dp/0072431881 |
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| library(ggplot2); theme_set(theme_bw()) | |
| library(scales) | |
| price_df$TitleTrunc = paste0(substring(price_df$TitleTrunc, 1, 30), ifelse(nchar(price_df$Title) > 30, "...", "")) | |
| ggplot(price_df, aes(Date, Price)) + | |
| geom_step() + geom_point() + facet_wrap(~ TitleTrunc, scales = "free_y") + | |
| scale_y_continuous(labels = dollar) + theme(axis.text.x = element_text(angle = 90, vjust = 0)) |
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