R task, web scraping - r

Question

I share my solution for the task, however, I get an error and cannot find the reason. Anyone can help with it?
Data download 1.1 Collect links Data on the Stack Overflow user survey is available on the Stack Overflow website. Create a web scraper that collects the links to the survey files. Select only the links to the surveys from 2017 to 2021.
lst_nodes <- "https://insights.stackoverflow.com/survey/" %>%
read_html() %>%
html_nodes(".js-download-link")
lst_url <- lst_nodes[1:5] %>%
html_attr("href")
print(lst_url)
Complete the function to download the data files from the URLs that extracted.
fun_download <- function(url) {
year <- # extract year from url
zip_file <- paste0("file_", year, ".zip")
zip_dir <- paste0("dir_", year)
download.file(url, zip_file)
unzip(zip_file, exdir = zip_dir, files = "survey_results_public.csv")
out <- read_csv(file.path(zip_dir, "survey_results_public.csv"), col_types = cols(.default = "c")) %>%
mutate(Year = year, ResponseId = row_number())
return(out)
year <- sub(".*[^0-9]([0-9]+)\\.zip$", "\\1", lst_url)
}
Apply the function to the URLs that you extracted and generate a data frame that contains the data from all surveys.
Save the data frame. Note: The read_csv command in the function seems to keep the downloaded csv files locked after reading. So once you tried to open the csv files, you cannot delete them. To overcome this lock, restart the R session.
Best to save the data so that you have to run the download and importing only once.
alldf <- lapply(lst_url, fun_download)
That is all I did so far...but it seems something is wrong

Answer 1

My suggestion to use year <- sub(.) needs to be put in context of the function itself, using its url only. This works.
fun_download <- function(url) {
stopifnot(length(url) == 1L) # just a safeguard
year <- sub(".*[^0-9]([0-9]+)\\.zip$", "\\1", url)
zip_file <- paste0("file_", year, ".zip")
zip_dir <- paste0("dir_", year)
download.file(url, zip_file)
unzip(zip_file, exdir = zip_dir, files = "survey_results_public.csv")
out <- readr::read_csv(file.path(zip_dir, "survey_results_public.csv"), col_types = readr::cols(.default = "c")) %>%
mutate(
Year = year,
ResponseId = row_number()
)
return(out)
}
fun_download(lst_url[[1]])
# trying URL 'https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2021.zip'
# Content type 'application/zip' length 8825103 bytes (8.4 MB)
# downloaded 8.4 MB
# # A tibble: 83,439 x 49
# ResponseId MainBranch Employment Country US_State UK_Country EdLevel Age1stCode LearnCode YearsCode YearsCodePro DevType
# <int> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr>
# 1 1 I am a deve~ Independen~ Slovakia NA NA Seconda~ 18 - 24 y~ Coding Bo~ NA NA Develop~
# 2 2 I am a stud~ Student, f~ Netherl~ NA NA Bachelo~ 11 - 17 y~ Other onl~ 7 NA NA
# 3 3 I am not pr~ Student, f~ Russian~ NA NA Bachelo~ 11 - 17 y~ Other onl~ NA NA NA
# 4 4 I am a deve~ Employed f~ Austria NA NA Master?~ 11 - 17 y~ NA NA NA Develop~
# 5 5 I am a deve~ Independen~ United ~ NA England Master?~ 5 - 10 ye~ Friend or~ 17 10 Develop~
# 6 6 I am a stud~ Student, p~ United ~ Georgia NA Bachelo~ 11 - 17 y~ Other onl~ NA NA NA
# 7 7 I code prim~ I prefer n~ United ~ New Ham~ NA Seconda~ 11 - 17 y~ Other onl~ 3 NA NA
# 8 8 I am a stud~ Student, f~ Malaysia NA NA Bachelo~ 11 - 17 y~ School;On~ 4 NA NA
# 9 9 I am a deve~ Employed p~ India NA NA Bachelo~ 18 - 24 y~ Coding Bo~ 6 4 Develop~
# 10 10 I am a deve~ Employed f~ Sweden NA NA Master?~ 11 - 17 y~ School 7 4 Data sc~
# # ... with 83,429 more rows, and 37 more variables: OrgSize <chr>, Currency <chr>, CompTotal <chr>, CompFreq <chr>,
# # LanguageHaveWorkedWith <chr>, LanguageWantToWorkWith <chr>, DatabaseHaveWorkedWith <chr>, DatabaseWantToWorkWith <chr>,
# # PlatformHaveWorkedWith <chr>, PlatformWantToWorkWith <chr>, WebframeHaveWorkedWith <chr>, WebframeWantToWorkWith <chr>,
# # MiscTechHaveWorkedWith <chr>, MiscTechWantToWorkWith <chr>, ToolsTechHaveWorkedWith <chr>, ToolsTechWantToWorkWith <chr>,
# # NEWCollabToolsHaveWorkedWith <chr>, NEWCollabToolsWantToWorkWith <chr>, OpSys <chr>, NEWStuck <chr>, NEWSOSites <chr>,
# # SOVisitFreq <chr>, SOAccount <chr>, SOPartFreq <chr>, SOComm <chr>, NEWOtherComms <chr>, Age <chr>, Gender <chr>,
# # Trans <chr>, Sexuality <chr>, Ethnicity <chr>, Accessibility <chr>, MentalHealth <chr>, SurveyLength <chr>, ...
From here, use lapply(., fun_download) to produce a list of frames.
list_of_frames <- lapply(lst_url, fun_download)
# trying URL 'https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2021.zip'
# Content type 'application/zip' length 8825103 bytes (8.4 MB)
# downloaded 8.4 MB
# trying URL 'https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2020.zip'
# Content type 'application/zip' length 9908290 bytes (9.4 MB)
# downloaded 9.4 MB
# trying URL 'https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2019.zip'
# Content type 'application/zip' length 18681322 bytes (17.8 MB)
# downloaded 17.8 MB
# trying URL 'https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2018.zip'
# Content type 'application/zip' length 20022841 bytes (19.1 MB)
# downloaded 19.1 MB
# trying URL 'https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2017.zip'
# Content type 'application/zip' length 9576818 bytes (9.1 MB)
# downloaded 9.1 MB
And a terse summary to show what they hold:
lapply(list_of_frames, function(z) z[1:2, 1:4])
# [[1]]
# # A tibble: 2 x 4
# ResponseId MainBranch Employment Country
# <int> <chr> <chr> <chr>
# 1 1 I am a developer by profession Independent contractor, freelancer, or self-employed Slovakia
# 2 2 I am a student who is learning to code Student, full-time Netherlands
# [[2]]
# # A tibble: 2 x 4
# Respondent MainBranch Hobbyist Age
# <chr> <chr> <chr> <chr>
# 1 1 I am a developer by profession Yes NA
# 2 2 I am a developer by profession No NA
# [[3]]
# # A tibble: 2 x 4
# Respondent MainBranch Hobbyist OpenSourcer
# <chr> <chr> <chr> <chr>
# 1 1 I am a student who is learning to code Yes Never
# 2 2 I am a student who is learning to code No Less than once per year
# [[4]]
# # A tibble: 2 x 4
# Respondent Hobby OpenSource Country
# <chr> <chr> <chr> <chr>
# 1 1 Yes No Kenya
# 2 3 Yes Yes United Kingdom
# [[5]]
# # A tibble: 2 x 4
# Respondent Professional ProgramHobby Country
# <chr> <chr> <chr> <chr>
# 1 1 Student Yes, both United States
# 2 2 Student Yes, both United Kingdom
If you need to assign names (such as the URL used to derive each dataset), then perhaps this, which adds a $url field to each frame.
list_of_frames <- Map(function(x, u) transform(x, url = u), list_of_frames, lst_url)
Data
library(rvest)
lst_nodes <- read_html("https://insights.stackoverflow.com/survey/") %>%
html_nodes(".js-download-link")
lst_url <- html_attr(lst_nodes [1:5], "href")
lst_url
# [1] "https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2021.zip"
# [2] "https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2020.zip"
# [3] "https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2019.zip"
# [4] "https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2018.zip"
# [5] "https://info.stackoverflowsolutions.com/rs/719-EMH-566/images/stack-overflow-developer-survey-2017.zip"