Phi range

[szepfalvibalint]

Hello,

I am using pythiaplotter to read in a vast amount of HepMC event files from Pythia8 for analysis. I have discovered a bug in calculating phi for particles. The math.asin functions have output values from -pi/2 to pi/2 (1st and 4th quarter plane), whereas the Pythia phi values range from -pi to +pi. The problem is easy to fix with something like:
if px<0:
if py>0: # we are in the second plane quarter
phi = math.pi - phi
if py<0: # we are in the third plane quarter
phi = -math.pi - phi
Please take a look at it.