Empty maps and reference data
In short: An empty map, or one with nodes but no links, isn't an error. It means your corpus doesn't hold what that map type is built from, or a slice or threshold removed everything, and SciNodes tells you which. Citation, Co-citation and Bibliographic Coupling maps need reference data, which isn't included when publications come from the catalog. Click Fetch reference data once for the project, wait a few minutes, then build the map again.
What each map type needs
| Map type | Built from | Empty when |
|---|---|---|
| Citation | Reference data | No reference data, or no publication cites another publication that is also in your corpus. |
| Co-citation | Reference data | No reference data, or no two cited publications are ever cited together. |
| Bibliographic Coupling | Reference data | No reference data, or no two publications cite the same publication. |
| Co-authorship | Author lists (and affiliations for organizations or countries) | Publications have no authors or no usable affiliations. |
| Keyword Co-occurrence | Author keywords, index keywords or MeSH terms | Publications carry none of the chosen keywords. |
| Term Co-occurrence | Titles, abstracts and keywords you chose | The chosen fields have no usable terms. |
Maps by venue need venue information on the publications.
What you might see
- A "No … to build" dialog right after you plot a map, for example "No citation to build". Nothing was created, and the dialog explains why. If reference data can help, it offers Fetch reference data.
- "Nothing to map" on the stage, with the reason underneath (or "Add more references to generate map").
- A banner over a map that has nodes but no links. It gives the reason and, when it can help, a Fetch reference data button. Click × to dismiss it. While a fetch runs it says "Reference data is still being fetched — this map will have links once it finishes."
- "Fetching reference data" when you start a citation, co-citation or coupling map while a fetch is running, for example "A citation map is built from reference data, which is still being fetched for this project. It will be available once the fetch finishes." Wait, then build again.
- In Expert Mode, the three reference-based types are greyed out during a fetch, with the note "Citation, co-citation and bibliographic coupling need reference data, which is still being fetched."
Fetch reference data
- Click Fetch reference data in the dialog or the banner.
- Watch the progress: "Looking up publications", "Reading reference lists", "Fetching cited publications" and "Linking references", each with a percentage. You can close the dialog; the fetch keeps running.
- When it finishes you see "Linked N references across N publications."
- Click Build the map in the dialog. If you started from a banner on an existing map, plot that map again from the Query Bank or Expert Mode.
The dialog explains: "Reference lists aren't included when publications are imported from the catalog. Fetching them looks up what every publication cites — this takes a few minutes for a corpus this size and only needs doing once."
SciNodes may already be fetching in the background, for example after you add publications. Then you see the progress instead of the button. Existing maps don't change when a fetch finishes; build a new map to use the new data.
Common reasons and fixes
Many messages start with "None of the publications in this corpus", "Only some of the publications in this corpus" or "All publications in this corpus", so you can tell how much is missing.
| Message (shortened) | What to do |
|---|---|
| "This project has no publications yet. Add publications to the corpus first." | Add publications. |
| "… carry a resolved reference list, which is what a citation map is built from." | Click Fetch reference data. |
| "… carry references, and none of them resolve to another publication in this corpus, so there is nothing to link." | Citation maps only link two publications you both hold. Add the cited publications (see Selecting, merging and excluding), or try a Co-citation or Bibliographic Coupling map. |
| "… no two of those cited publications are ever cited together …" or "… no two publications share one …" | The overlap isn't there. If it adds "Fetching the missing reference lists may reveal some.", fetch reference data. Otherwise grow the corpus or choose another map type. |
| "… carry author keywords, which is what a keyword co-occurrence map is built from." | Try Index Keywords, or a Term Co-occurrence map from titles and abstracts. |
| "No publication in this corpus matches the filters you applied (…). Widen them and generate again." | Loosen the corpus slice. |
| "Nothing in this corpus meets the minimum of N. Lower it in the map's advanced settings and generate again." | Lower the minimum in Expert Mode → Thresholds. |
| "None of the publications on this map cite each other, so it has no links. Citation maps only draw edges between two publications you hold in this corpus." | As above: add cited publications or try co-citation or coupling. |
| "No pair of the nodes on this map is connected, so it has no links." | Grow the corpus, widen the slice, or lower thresholds. |
Troubleshooting
- "Could not start fetching references." Try again in a moment.
- "Fetching references failed." The fetch stopped. Click Fetch reference data again later.
- The button doesn't appear. Reference data can't help with this map type or reason, for example missing keywords or authors. Use the fixes above.
- A citation map still has few links after fetching. Most cited publications may not be in your corpus. Use a co-citation map, which includes cited publications outside your corpus, or add the cited publications.
FAQ
Why are citation maps empty for catalog imports?
Publications found through Suggest or Discover arrive without their reference data. Fetching it once per project fills it in.
What if my publications came from uploaded files?
The same checks apply. If a citation-based map is empty or has no links and fetching can help, SciNodes offers Fetch reference data.
Does fetching reference data change my corpus?
It links your publications to the publications they cite, which is what citation-based maps need. Your existing maps stay as they are until you build new ones.
How long does it take?
A few minutes for most corpora. It runs in the background, so you can keep working.