In today's Guardian are details about some of the interactive tools that will be available for viewers who watch Thursday evening's first prime-ministerial debate at It describes a range of "sentiment" tools that will be deployed to measure live responses to the discussion between leaders of the three main parties: Gordon Brown, David Cameron and Nick Clegg. In visualisation terms the most interesting of these devices are:

Twitter 'sentiment' tool

This will track posts made by 5,000 Twitter users and label each tweet made about the leaders based on a sentiment scale of 1 to 5. These values will then be aggregated each minute to form a dynamic 'score' of each leader during the debate which will be presented with a directional arrow alongside a picture of each leader.

The Worm

Alongside a live stream of the debate an audience reaction tool will track the views of a panel who will use handheld devices to register their impressions. These will be displayed using a worm graph.

The ‘Tesco’
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