R: Strange trig function behavior

Question

As a Matlab user transitioning to R, I have ran across the problem of applying trigonometric functions to degrees. In Matlab there are trig functions for both radians and de

Answer 1

Looks like it's working fine to me. The value for pi probably isn't precise enough, so you are getting a very close estimate. If you think about it, 6.123234e-17 and -1.836970e-16 are very very close to 0, which is what the answer should be.

Your problem lies in the fact that while 90*pi/180 = pi/2 on paper, in computers, we use floating point numbers. I'm not sure what R/matlab use, but I'd definitely guess either a 32 bit or 64 bit floating point number. And you can only fit so much information in that limited number of bits, so you can't store every possible decimal.

You could modify your function so that given 90 or 270, return 0.