scopus_search_plus.R

# Run `rscopus::scopus_search` as many times as necessary based on the number of results and the search quota. 

# Note. Before running the current function, the user must read in their Scopus API key confidentially 
# (see https://cran.r-project.org/web/packages/rscopus/vignettes/api_key.html). An error appears if the key 
# has not been read in.

scopus_search_plus = 
  
  function( query, 
            search_period,                     # single year or period (e.g., '2000-2010')
            quota = 5,                         # Scopus API quota
            view = c('STANDARD', 'COMPLETE'),  # see https://cran.r-project.org/web/packages/rscopus/rscopus.pdf
            inst_token = NULL,                 # see https://cran.r-project.org/web/packages/rscopus/rscopus.pdf
            verbose = TRUE                     # print progress in R console
  ) {
    
    require(rscopus)
    
    # Error if API key missing
    if(!have_api_key()) {
      stop('The login key for the Scopus API has not been read in. Find out more at \n',
           '  https://cran.r-project.org/web/packages/rscopus/vignettes/api_key.html')
    }
    
    require(dplyr)
    
    # Use tryCatch() to handle errors in scopus_search
    res = tryCatch({
      
      if(is.null(inst_token)) {
        scopus_search(query = query, max_count = quota, count = quota, 
                      date = search_period, view = view,
                      verbose = verbose)
      } else {
        scopus_search(query = query, max_count = quota, count = quota, 
                      date = search_period, view = view,
                      headers = inst_token_header(inst_token), 
                      verbose = verbose)
      }
      
    }, error = function(e) {  # Print error message to console
      print(paste("Error in nested function 'scopus_search':", e$message))
    })
    
    total_results = 0 : res$total_results
    
    chunks = total_results[seq(1, length(total_results), quota)]
    
    results = data.frame(author = as.character(), date = as.character(), 
                         title = as.character(), publication = as.character(), 
                         doi = as.character())
    
    for(i_chunk in 1 : n_distinct(chunks)) {
      
      # Use tryCatch() to handle errors in scopus_search
      res = tryCatch({
        
        if(is.null(inst_token)) {
          scopus_search(query = query, max_count = quota, count = quota, 
                        start = chunks[i_chunk], date = search_period, 
                        view = view, verbose = verbose)
        } else {
          scopus_search(query = query, max_count = quota, count = quota, 
                        start = chunks[i_chunk], date = search_period, 
                        view = view, headers = inst_token_header(inst_token), 
                        verbose = verbose)
        }
      }, error = function(e) {  # Print error message to console
        print(paste("Error in nested function 'scopus_search':", e$message))
      })
      
      for(i_entry in 1 : length(res$entries)) {
        
        author = res$entries[[i_entry]]$`dc:creator`
        date = res$entries[[i_entry]]$`prism:coverDisplayDate`
        title = res$entries[[i_entry]]$`dc:title`
        publication = res$entries[[i_entry]]$`prism:publicationName`
        doi = res$entries[[i_entry]]$`prism:doi`
        
        i_results = data.frame( author = ifelse(!is.null(author), author, NA), 
                                date = ifelse(!is.null(date), date, NA), 
                                title = ifelse(!is.null(title), title, NA), 
                                publication = ifelse(!is.null(publication), publication, NA), 
                                doi = ifelse(!is.null(doi), doi, NA) )
        
        results = rbind(results, i_results)
      }
    }
    return(results)
  }