Graph Element Questions

Hi,

We are currently evaluating your WPF chart control and so far we are very pleased with it. We have a few questions that we would like to ask you though.

1. As we add our line series dynamically, we also need to add AlternativeYAxes dynamically. Each Series need to be bound/associated with a specific AlternativeAxis. Because some of our lines might have values ranging between 0-5000 and some between 40-50 they need to be scaled to individual Y-axes. We want to do this by code and not in Xaml. Is this possible, do you have any guidlines/recommendations?
2. We would like to show our alternative axes as an overlay over the graph as opposed to have them placed on the side of the graph (left,right etc..). Is this possible?
3. As our series are represented in other views as well we would like to bind the Graph's selected line to a dependancy property that can be shared between the views. What is the best practise to solve this?

Best regards

Hello and thanks for evaluating our WPF chart control. It is great to hear that you are pleased with it.

1. Yes this is possible. You can dynamically add ChartAxis objects to the AlternativeYAxes collection in code which will update the chart display accordingly. One thing I would suggest is that you encapsulate all the logic for updating the AlternativeYAxis collection in a single class. On your model object, expose a property that includes a collection of objects that describe the axes you want the chart to display. The alternative axis manager class you make could then listen to this property and then translate this to the ChartAxis objects that need to be added to the AlternativeYAxis collection. I haven't tried this in this particular scenario, but this is the general MVVM approach to this question. Overall, how you do this is up to how you want to structure your application. Whatever approach you take, let me know if you run into any troubles.
2. This is currently not possible, but it is a feature that I've always wanted to add to the chart control. Please send some images to help me get a full understanding of the behaviour you would like in your application. I'll have a look at if we can add this to the chart control for you, but I can't make any promises for this feature as it may be quite a mission to implement.
3. This partly depends on how you are structuring your application. If you could send my a sample project that roughly demonstrates the model structure you have and how you are binding this up to the charts, than I'll be happy to look through it and recommend how to tackle this. Overall, the solution would be to store the selected state of each series in your application model somehow. This selected state would be accessible to all views making it easy for all views to correctly display the selected series.

Jason Fauchelle

Hello Jason and thank you for answering so quickly

Regarding question 1. Do you have an example of when you dynamically add AlternativeYAxes and still stick to the MVVM convention? Since AlternativeYAxes can't be bound and we don't want to access the Graph directly from code if possible.

Best regards

Hello

I don't have an example for this specifically, but here is a link to a similar problem to this: http://blog.functionalfun.net/2009/02/how-to-databind-to-selecteditems.html

Basically, you create an attached property that contains the logic for syncing an observable collection to another collection. On your model, you could have an observable collection that provides the alternative axis information. In xaml you'd use the attached property on the Chart control to bind to the property on the model that provides the observable collection. Within this attached property, you'd hook into the observable collection, and when it changes, update the alternative axis collection of the Chart control which you'll have access to within the attached property.

This does mean the chart is being manipulated in code, but it is all nicely wrapped up in an attached behaviour which is the most MVVM solution to this scenario that I know of. Give this a go, and let me know if you need help with this.

Jason Fauchelle

Hello Jason

Thank you so much. This helped me to solve the problem.

I have some other questions. The placing/spacing of the graphs horizontal minor tickmarks behaves weird. I've attached a cropped screenshot that illustrates the problem. The lines are not evenly spaced.

I've also discovered that when zooming in the graph using the zoombox, it looses the values on the X-axis and the lines disappears. Even if you zoom out again, the lines are gone.

I also wonder if one can turn off the automatic horizontal scaling of the graph. We want to be able to show a certain timespan even if there are no values in the plotted series for that timespan. Our graph always crops the timespan after the plotted values.

Best regards.

Hello

It sounds like you may not have the latest build as these issues should be resolved. You can get the latest build from here: http://www.mindscapehq.com/products/wpfelements/nightly-builds. This build is updated every night which means you can get bug fixes and new features very rapidly, even for the trial version.

You can override the automatic axis range by setting the Minimum and Maximum properties of the X axis manually. In your case you'd set these to be DateTime values.

Jason Fauchelle