Hi - is anyone aware of any built-in function in python that allows to interactively select data ranges (by clicking & dragging) on plots and if possible print tangents on these plots as the user-defined range is adjusted? See picture below. 
Hi Peter,
PyQtGraph allows you to implement something like that easily; e.g. have a look at:
Interactive Data Selection Controls — pyqtgraph 0.12.1 documentation
You can also ‘fully’ control the interaction between mouse, buttons/keys and graphs on a lower level using the ‘events’ triggered by the underlying Qt system (and handled by PyQtGraph).
If you want to see an example of what can be done this way, feel free to have a peek at the following video - the demo software shown in there, was developed by me using Qt (GUI) and PyQtGraph (plots) based on a Blythooon installation - it is unfortunately just commented in German yet, but I think, you can get a good impression by just watching the video part:
You can skip the first 4:30 minutes intro if you want…
Have Fun, Dominik
Hi Dominik. Thanks for your response - i’ll spend some time looking into this. Python is fairly new to me so i see this as a long term project 
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