LabVIEW
Graph Challenge
I'm looking for suggestions on how to create a graph which is easy to imagine, but appears difficult to implement in LabVIEW.
- first, imagine a XY graph with a single group of three plots. These three plots never intersect (they were calculated as max, min, and mean from each row of a dataset). I want to fill the plot between the max and the min line with a solid color and still have the mean line visible.
So far, it's easy; plot the mean first, and then add the max and min lines, and fill between them.
- now, imagine several more groups of three lines similar to the first group. Unfortunately, these groups may intersect each other.
I'd like to be able to see every group, and even better, shade the areas where the groups intersect.
The simple solution is to make the fill color semi-transparent. Someone, please tell me that this is possible in 8.2.1 🙂 I've considered a complicated solution where I create a separate set of plots for each contiguous section of a group, but this gets complicated very quickly (for two groups, it seems pretty managable, but as the number of groups increases, and the potential number of distinct overlapping regions grows, the number of plots required skyrockets).
I've also attempted to do this using a .NET library called Zedgraph. It can make very nice graphs and use an alpha channel to make the fill area semi-transparent; however, its ability to fill between two plots appears to be very limited.
I am open to all options: other graphing libraries, trying some magic with the picture control, etc.
I've attached a vi containing a XYgraph control with some data. I've laid it out like I described at the beginning of this question. This particular dataset doesn't overlap too much, but I need to be able to handle arbitrary datasets.
I hope this makes sense. Thanks.
Chris
- first, imagine a XY graph with a single group of three plots. These three plots never intersect (they were calculated as max, min, and mean from each row of a dataset). I want to fill the plot between the max and the min line with a solid color and still have the mean line visible.
So far, it's easy; plot the mean first, and then add the max and min lines, and fill between them.
- now, imagine several more groups of three lines similar to the first group. Unfortunately, these groups may intersect each other.
I'd like to be able to see every group, and even better, shade the areas where the groups intersect.
The simple solution is to make the fill color semi-transparent. Someone, please tell me that this is possible in 8.2.1 🙂 I've considered a complicated solution where I create a separate set of plots for each contiguous section of a group, but this gets complicated very quickly (for two groups, it seems pretty managable, but as the number of groups increases, and the potential number of distinct overlapping regions grows, the number of plots required skyrockets).
I've also attempted to do this using a .NET library called Zedgraph. It can make very nice graphs and use an alpha channel to make the fill area semi-transparent; however, its ability to fill between two plots appears to be very limited.
I am open to all options: other graphing libraries, trying some magic with the picture control, etc.
I've attached a vi containing a XYgraph control with some data. I've laid it out like I described at the beginning of this question. This particular dataset doesn't overlap too much, but I need to be able to handle arbitrary datasets.
I hope this makes sense. Thanks.
Chris
Message Edited by C. Minnella on 04-22-2007 10:58 PM
(OK, you can disregard this. The transparency appears to be the issue here. My bad 
)
Just a thought, but have you checked out the example in the Example Finder called Limit Example.vi? You can just search for the keyword limit to find it. It shows an example of using a Fill Plot on a waveform graph. You can choose to plot one signal as being filled to another signal instead of just being a line. You can fill to positive or negative infinity, to zero, or to any other plot of your choice. It looks like you could use this to construct your graphs. To select a fill plot, just right click the plot in the legend and select Fill Base Line and then select the other plot to fill to. Would this suffice?
)Just a thought, but have you checked out the example in the Example Finder called Limit Example.vi? You can just search for the keyword limit to find it. It shows an example of using a Fill Plot on a waveform graph. You can choose to plot one signal as being filled to another signal instead of just being a line. You can fill to positive or negative infinity, to zero, or to any other plot of your choice. It looks like you could use this to construct your graphs. To select a fill plot, just right click the plot in the legend and select Fill Base Line and then select the other plot to fill to. Would this suffice?
Message Edited by Jarrod S. on 04-23-2007 10:47 PM
Okay, it looks like Ben showed me the way. I was all prepared to figure out how to use a picture control with multiple images for the plots averaged together, but if the guru of picture controls says there is another way, I'll take a look. I had to stare at the 3DGraph control for a while before I figured it out, but here's a pic. I used the max and min lines to define a surface as a single plot in a single plane (the Z's are all zero), and drew the mean line as a separate plot for each group. Set the transparency for the surfaces, set the graph to view the XY Plane (or any other...), and clean it up by dropping it on top of a normal graph control. I'll include a vi when I have an opportunity to clean the code up.
Message Edited by C. Minnella on 04-24-2007 07:33 AM
So, I decided to tackle this problem as an xControl. It was instructive. Here's an example of a program using my xControl. It is functional enough that I will use it in an application, but I'd love to hear some commentary on how it works. There seem to be some incredibly annoying race conditions inherent in the way xControls are implemented (I've heard LV9.0 will fix these...); I punted and went with Waits. I tried an approach with Semaphores, but it didn't really solve the problem as I can't wait on a semaphore until I'm already in the problem vi, which means it was called with the wrong Display State already (and waiting won't fix it). I started switching over to a queue based approach, but the problem would still be there because I can't force all interaction with the Display State case of the facade VI through my queue.
One thing I could have done to mitigate the problem is change the way the plot names get set, but I really wanted the control interface to work like the built-in controls (i.e., Active Plot... Plot Name). I guess my punt torched that thought, but its too late now...
Anyway, any comments would be appreciated. Use Example VI for a look. The code is in 8.20.
One thing I could have done to mitigate the problem is change the way the plot names get set, but I really wanted the control interface to work like the built-in controls (i.e., Active Plot... Plot Name). I guess my punt torched that thought, but its too late now...
Anyway, any comments would be appreciated. Use Example VI for a look. The code is in 8.20.
Message Edited by C. Minnella on 06-10-2007 11:30 PM
