RCVis can't open the only JSON file output by RCTab

[davidlbangs]

probably a user error, but this is the Output folder from running RCTab:

Note that RCVis says it imports RCTab JSON files. This was the only one and the instructions provided by RCVis don't explain

[davidlbangs]

2026-02-27_13-19_detailed_report.json

This is the file. It was the result of having done a Bottoms-Up multi-winner tabulation.

[artoonie]

Hi David, I can't reproduce this. It seems to upload just fine for me:

Given the error, it looks like maybe you didn't select a file at all?

[davidlbangs]

If I did had successfully select a file, it seems like the button would be disabled or the message would be different.

I tried it again and was able to upload the file. The descriptions in RCVis are free of mentions of "Threshold". I'm not sure why because the output file does mention threshold in every round. I'm not sure why it does - and how RCVis knows not to display the threshold, which it does/did do when it is embedded in RCV123 with bottoms up tabulation.

[artoonie]

The new RCTab format specifies a threshold in every round, since the threshold in STV can change each round. This update is very recent and RCVis hasn't yet updated to support it. It doesn't show any info about a threshold because there is no "global" threshold information, which is what RCVis is looking for.

I suppose a solution for bottoms-up is to simply omit a threshold rather than putting a zero. RCVis knows how to handle elections with no thresholds.

[davidlbangs]

There is no threshold in Bottoms Up tabulation. it is inapplicable. That is why we set it to zero. We do not draw a "Votes to win" line if it is bottoms up. You just eliminate candidates until the number left is equal to the number of winners.

[artoonie]

RCVis supports omitting a threshold. Will this work for your use case?

[davidlbangs]

Yes, I updated rcv123.org to omit the threshold for bottoms-up tabulated ballots. RCVis stopped mentioning thresholds, so I removed the warning that RCVis results may be unreliable for those ballots.

RCVis descriptions could be improved in many cases, but they do add value in a way that RCV123 results do not.