image.gallery.R

image.gallery <- function(url, ncol = 3L) {

## This function reformats the contents of a Craigslist search result URL
## into an image gallery, opened into the default browser
##
## Inputs:
##    - url:  a Craigslist search URL as created by search.url
##    - ncol: the number of columns for the output image gallery
##
## Output: none. As a side effect, a browser is opened.

   require(RCurl)
   require(stringr)
   require(R2HTML)

   scrap     <- getURL(url)
   adds      <- str_extract_all(scrap, '<p class="row">.*?</p>')[[1]]

   pic.str   <- str_extract(adds, 'id="images:.*?jpg"')
   pic.base  <- str_replace(pic.str, 'id="images:(.*jpg)"', "\\1")
   pic.url   <- paste("http://images.craigslist.org/", pic.base, sep = "")
   pic.tags  <- paste('<img src="', pic.url, '" alt="', pic.url, '" ',
                      'style="width:100%"/>', sep = "")
   adds      <- paste(pic.tags, '<BR>', adds)
   add.mat   <- suppressWarnings(matrix(adds, ncol = ncol, byrow = TRUE))

   html <- HTMLInitFile()
   HTML(add.mat, innerBorder = 1, file = html)
   HTMLEndFile(html)
   browseURL(paste("file://", html, sep = ""))
}

pick.category.R

.pick.category <- function() {

## This function prompts a menu for selecting a search category and returns
## the corresponding 3-letter code used by Craigslist

   categories <- read.table(textConnection("

    CODE = DESCRIPTION

    sss = all for sale / wanted
    ata = antiques
    ppa = appliances
    ara = arts+crafts
    pta = auto parts
    baa = baby+kids
    bar = barter
    haa = beauty+health
    bia = bikes
    boo = boats
    bka = books
    bfa = business
    cta = cars+trucks
    ema = cd/dvd/vhs
    moa = cell phones
    cla = clothing+accessories
    cba = collectibles
    sya = computers
    ela = electronics
    gra = farm+garden
    zip = free stuff
    fua = furniture
    gms = garage sales
    foa = general for sale
    hsa = household
    wan = items wanted
    jwa = jewelry
    maa = materials
    mca = motorcycles
    msa = musical instruments
    pha = photo+video
    rva = recreational vehicles
    sga = sporting goods
    tia = tickets
    tla = tools
    taa = toys+games
    vga = video gaming"), header = TRUE, sep = "=", strip.white = TRUE,
                          stringsAsFactors = FALSE)

   selected.idx <- menu(categories$DESCRIPTION, title = "pick a category:")

   return(categories$CODE[selected.idx])
}

search.craigslist.R

search.craigslist <- function(site.url = "http://atlanta.craigslist.org",
                              ncol     = 3L) {

## This function prompts the user with questions for searching Craigslist
## (search items, price, etc.) and displays the search results into an image
## gallery.
##
## Inputs:
##    - site.url: Craigslist site URL
##    - ncol:     the number of columns for the output image gallery
##
## Output: none. As a side effect, a browser is opened.

   query      <- readline("search Craigslist for: ")
   category   <- .pick.category()
   title.only <- readline("search titles only (press 1 or ENTER to skip): ")
   min.price  <- readline("min price (press ENTER to skip): ")
   max.price  <- readline("max price (press ENTER to skip): ")
   pic.only   <- readline("pic only  (press 1 or ENTER to skip): ")

   title.only <- title.only == "1"
   min.price  <- as.integer(min.price)
   max.price  <- as.integer(max.price)
   pic.only   <- pic.only == "1"

   url <- search.url(query      = query,
                     site.url   = site.url,
                     category   = category,
                     title.only = title.only,
                     min.price  = min.price,
                     max.price  = max.price,
                     pic.only   = pic.only)

   image.gallery(url, ncol = ncol)
}

search.url.R

search.url <- function(query,
                       site.url   = "http://atlanta.craigslist.org",
                       category   = "sss",
                       title.only = TRUE,
                       min.price  = integer(0),
                       max.price  = integer(0),
                       pic.only   = TRUE) {

## This function creates a search URL on Craigslist.
##
## Inputs:
##    - query:      search string
##    - site.url:   Craigslist site URL
##    - category:   a three-letter code for the category; some examples
##                   "sss": all for sale/wanted, "zip": free stuff
##    - title.only: boolean for restricting the search to add titles
##    - min.price   minimum price
##    - max.price:  maximum price
##    - pic.only:   boolean for restricting the search to adds with pics
##
## Output: a string representing a Craigslist search URL

   search <- list(query    = gsub(" ", "+", query),
                  catAbb   = category,
                  srchType = ifelse(title.only, "T", "A"),
                  minAsk   = as.integer(min.price),
                  maxAsk   = as.integer(max.price),
                  hasPic   = as.numeric(pic.only))

   valid <- sapply(search, length) > 0L

   search.str  <- paste(names(search)[valid], search[valid],
                        sep = "=", collapse = "&")
   search.url  <- paste(site.url, "/search/sss?", search.str, sep = "")

   return(search.url)
}