> I would like to know how to retrieve the online data during the experiment so 
> that I can create my own custom plot. I execute my own frontend.exe to start the 
> experiment. I can get a midas file after the experiment, but I am not sure about 
> how to retrieve the online data. I know that rootana can help us to get the 
> online plots, but the instructions in rootana is not clear. Can anyone give me 
> some suggestion?  Thank you.

The current package for analyzing MIDAS data is the "m" analyzer, usually in the manalyzer subdirectory of your midas package, 
but it can also be used stand-alone without MIDAS.

There is several examples:

manalyzer_example_cxx.cxx - a simple "c++" example shows how to extra midas bank data
manalyzer_example_root.cxx - how to create ROOT histograms (that you can see online using jsroot)
manalyzer_example_root_graphics.cxx - how to create a ROOT graphical program (obsoleted by jsroot, but still possible)
manalyzer_example_flow*.cxx - more advanced examples on using a flow analyzer

Documentation is in README.md

Unfortunately there is no tutorial or 5 min youtube explainer, each experiment needs are very different, there is no way to 
write a one-size-fits-all recipe.

Please take a look at the existing examples first, then send me a PM with any additional questions (or ask here). If you can 
explain what kind of data you have and how you want to look at it, I should be able to guide you through writing an appropriate 
manalyzer module.

K.O.