Can I Change The Grid Line Of Polar Plot To Log Scale?

[smobius01@msn.com]

I want to plot an antenna signal intensity graph with polar plot in LabVIEW 7.1. Data are signal strength in dB (y-axis, log scale) vs. degree (x-axis). Can I change the step of circular gird line into log scale and the degree in clockwise rotation?

[altenbach]

Look at the "polar attrubutes" input. One of the cluster elements is a boolean name "log?(F)". Set it to TRUE and see what happens. 🙂

[smobius01@msn.com]

Yes, the ploted data can change to log scale, but the step of the circles cannot change as expected. I want to change the circle in log scale gradient as 0, -2, -4, -6, -8, -10, -20, -40, -60.

[altenbach]

All the code inside the "polar plot.vi" subVI is plain LabVIEW. You should be able to modify it for your exact purpose and save it under a new name.

[smobius01@msn.com]

Thanks for your suggestion, but I want to output the log scale polar plot as attached file. I have searched the polar plot sub-vi setting but it seems no option like this. Do you have any idea about the auto scale operation? It is most likely the control centre of the plot scale. 

[altenbach]

I did not say there was a direct option to do what you want. I only said that the guts of the polar plot VI are not hidden from the user and can be modified to do anything you want with some creative code changes!

The output is a plain picture indicator and you have full freedom to draw any kinds of circles, lines, and points any way you want. All this has already been done for a simple polar plot inside "polar plot.vi" and associated subVIs. Simply take the entire hierarchy and save it under a new name elsewhere. Now you can surgically hack into some of the existing VIs and modify it for your purpose by changing the actual code. For example, inside "draw polar grids", you would modify the way the circles are mapped to the graph. Inside "plot polar data", you would modify "map value to pixel". I don't think it would be to difficult once you are a bit familiar with picture commands. Have you tried?