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I'm writing a program that lets me animate the orbits of the planets in Matlab. This is working, but I would like to display the amount of times they fully went around the sun in a certain time lapse. I've been doing this by comparing the position they begin with with their current position: abs(current_position - begin_position < precision. But here's my problem: this precision is very different for each planet and their data. Like for Jupiter I have to set this precision to 0.2, while for Neptune it has to be 0.001, so I can't just say precision = 0.2, because it generates faults with my other planets if I do so. Is there another way to compare these numbers or another way to achieve this? I've been trying to use angles also, but that didn't worked out quite well.

Thanks in advance.

Griet De Clercq
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    What about `abs(current_position/begin_position - 1) < precision` as now you could stick with a single precision as you are comparing them relatively? – Dan Apr 12 '13 at 15:53
  • Are their respective positions proportional to the precision? I.e. does a larger position correlate to a larger precision; if so than Dan's solution should work. If not then you could test each planet for their respective precisions and then store these values in a vector. – JustinBlaber Apr 12 '13 at 16:07

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I would use a vector to store the precision of each planet. However you will have to check in each iteration if the position match and then increase a counter for the number of orbits.

Why angles give you problems? You can accumulate the angle, subtract the initial angle and then calculate a modulus 360 (or 2*pi) to know the number of orbits.