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  how does CD handle data amalgamation and imagemaps
Posted by Paul on Mar-18-2011 20:22
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Hi Peter

I wonder if you could explain a little about how chartdirector deals with data amalgamation and imagemap content.

My situation is that my bar graph is 700px wide. The x-axis is time and covers a period of one day. I have 1440 data points collected during that one day and and array of this data is what I am giving chart director to plot. I am also asking for an imagemap to be generated for the data so I can use tooltips as the user mouses over the graph.

How does CD take my 1440 data points and reduce them down to fit into a 700px wide space - obviously no more than one bar can be plotted per pixel so I would see a maximum of 700 of my data points plotted - I know that this is not what happens and assume some sort of data amalgamation is taking place. If this is the case could you also explain how the imagemap handles this situation - does it contain data for all 1440 points or does it also get reduced down so only one imagemap co-ordinate exists per pixel?

Hope that is clear enough for you to see what I am trying to understand. Thanks as always for any help you can give.

P.

  Re: how does CD handle data amalgamation and imagemaps
Posted by Peter Kwan on Mar-19-2011 01:53
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Hi Paul,

ChartDirector does not automatically perform data "amalgamation". For your case, ChartDirector will draw all 1440 bars, even if they may overlap, and it will auto create 1440 regions for the image map.

Data "amalgamation", or data aggregation, is usually the function of the database. For a bar chart, if two bars are plotted at the same position, you probably will see the taller of the two bars. So when you create the database query, you can use an aggregate query (in SQL this is done using a "GROUP BY" clause in the query) to aggregate two values into one by taking the maximum value. This reduces your data to 720 values, which better suit the resolution of the chart.

Hope this can help.

Regards
Peter Kwan

  Re: how does CD handle data amalgamation and imagemaps
Posted by Paul on Mar-21-2011 17:13
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Thank you Peter - very useful as usual

Kind regards

Paul