All distributions should have RNGs

[agarie]

Some of the currently supported distribution don't have RNGs, e.g. Fisher-Snedecor and exponential.

• [ ] Triage the code to see which distributions lack a RNG.
• [ ] Prepare a plan to implementing them. Can we copy some implementation or should we roll our own? (this is actually quite easy for the ones we currently support)

[envp]

Currently these are the distribution with an rng method (grep -rl def\ rng ./lib/distribution):

• [x] Chi-squared
• [x] Exponential
• [x] Logistic
• [x] Normal
• [x] Uniform

That leaves the following with no rng method defined:

• [ ] Beta
• [ ] Binomial
• [ ] Bivariatenormal
• [ ] F
• [ ] Gamma
• [ ] Hypergeometric
• [ ] Lognormal
• [ ] Normalmultivariate
• [ ] Poisson
• [ ] Student's T
• [ ] Weibull

Let me know if I missed something.

[agarie]

@vaibhav-y that's very good. Can you update the table in the README.md file? Just send a PR with that and I'll merge it.

[envp]

PR https://github.com/SciRuby/distribution/pull/34 added for README.

This PR doesn't consider changes uniform distribution since SciRuby/distribution hasn't merged it yet. I will rebase that PR and update the README there itself.

Edit: Please don't close this PR yet, I intend to use this to track the implementations for the rng methods which seem to be the only outstanding things as of now (apart from gamma distribution's Inverse CDF)

[agarie]

That's fine. I'll merge #34 as soon as it passes Travis.