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Thread: Dividing a circle into unequal parts (Like a pie graph)

  1. #1
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    Dividing a circle into unequal parts (Like a pie graph)

    Hello all!

    I am attempting a project that tracks the lunar cycle in a circular map, which looks like a pie chart. The problem I'm having is that "Lunar months" are not a nice even number. For instance the Lunar month of August 2018 is 29 days, 8 hours, and 4 minutes. If it were just a round 29 days that would be easy, but I'm having trouble accounting for the extra third-ish of a day.

    What I'm trying to devise is a circular map with spokes radiating from the center, creating triangle slices that consist of a lunar day. Therefore, 29 of these equal length days, but then a proportionally small 8hour and 4 minute slice. I'd like to do one of these for each month and the number of additional hours and minutes changes pretty dramatically so I was hoping someone could show me a methodology to calculate this myself for the future. I won't lie, I'm pretty uneducated. I've been using adobe Illustrator which has a great tool for this assuming your numbers are nice and round. I can simply enter into the rotation box 360/29 and get nice even slices. But this takes up the whole circle. I need 29 even slices PLUS the extra bit.

    If anyone is willing to help me with this I would be very appreciative. Thank you just the same for taking the time to read my request for help!
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  2. #2
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    Re: Dividing a circle into unequal parts (Like a pie graph)

    "29 days, 8 hours, and 4 min= 29 days, 8+ 4/60 hours= 29 days, 8.067 hours= 29.337 days."

    Do the same for each of the 12 months, then add them up to find the number of days in the year (which will be about 364.25 days, of course). Divide the number of days in each month by the number of days in the year (and those fractions should add to 1.00, of course). That will tell what fraction of the year each month is (and each should be close to 1/12). Multiply each of those fractions by 360 degrees to find what fraction of the complete disk on your circle map each month is. Finally, create your circle map by measuring each month's angle at the center of the circle.
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    Re: Dividing a circle into unequal parts (Like a pie graph)

    I apologize. I'm not trying to get a yearly map, I'm trying to get a monthly map. The problem is that last fraction of a day. I don't know how to get 29 equal slices PLUS that extra bit (so 30 slices total) to fit evenly into 360 degree.
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    Re: Dividing a circle into unequal parts (Like a pie graph)

    Hello

    Well 29 days, 8 hours and 4 minutes gives a total of 42244 minutes. Thus one day should make a wedge with an angle given by ((24*60)/42244)*360 which is roughly 12.27 degrees. The hours will then be (60/42244)*360 rounding to 0.51, and one minute will be 0.009. Which means you will have 29 wedges with an angle of 12.27 degrees each, totaling 355.88 degrees, and the last wedge having 4.12 degrees.
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