Starting values used in fitdistrplus4 days ago
1. Discrete distributions | 1.1. Base R distribution | 1.1.1. Geometric distribution | 1.1.2. Negative binomial distribution | 1.1.3. Poisson distribution | 1.1.4. Binomial distribution | 1.2. logarithmic distribution | 1.3. Zero truncated distributions | 1.4. Zero modified distributions | 1.5. Poisson inverse Gaussian distribution | 2. Continuous distributions | 2.1. Normal distribution | 2.2. Lognormal distribution | 2.3. Beta distribution (of the first kind) | 2.4. Other continuous distribution in actuar | 2.4.1. Log-gamma | 2.4.2. Gumbel | 2.4.3. Inverse Gaussian distribution | 2.4.4. Generalized beta | 2.5. Feller-Pareto family | The gradient with respect to $\theta, \alpha, \gamma, \tau$ is\begin{equation}\nabla\mathcal L(\mu, \theta, \alpha, \gamma, \tau) | 2.5.1. Transformed beta | 2.5.2. Generalized Pareto | 2.5.3. Burr | The survival function is$$1-F(x) = (1+(x/\theta)^\gamma)^{-\alpha}.$$Using the median $q_2$, we have$$\log(1/2) = - \alpha \log(1+(q_2/\theta)^\gamma).$$The initial value is\begin{equation}\alpha | 2.5.4. Loglogistic | 2.5.5. Paralogistic | 2.5.6. Inverse Burr | 2.5.7. Inverse paralogistic | 2.5.8. Inverse pareto | 2.5.9. Pareto IV | The first and third quartiles $q_1$ and $q_3$ verify$$((\frac34)^{-1/\alpha}-1)^{1/\gamma} = \frac{q_1-\mu}{\theta},((\frac14)^{-1/\alpha}-1)^{1/\gamma} = \frac{q_3-\mu}{\theta}.$$Hence we get two useful relations\begin{equation}\gamma | \frac{\log\left(\frac{(\frac43)^{1/\alpha}-1}{(4)^{1/\alpha}-1}\right)}{\log\left(\frac{q_1-\mu}{q_3-\mu}\right)},(#eq:pareto4gammarelation)\end{equation}\begin{equation}\theta | 2.5.10. Pareto III | Pareto III corresponds to Pareto IV with $\alpha=1$.\begin{equation}\gamma | \begin{equation}\theta | 2.5.11. Pareto II | 2.5.12. Pareto I | 2.5.13. Pareto | Pareto corresponds to Pareto IV with $\gamma=1$, $\mu=0$.\begin{equation}\theta | 2.6. Transformed gamma family | 2.6.1. Transformed gamma distribution | 2.6.2. gamma distribution | 2.6.3. Weibull distribution | 2.6.4. Exponential distribution | 2.7. Inverse transformed gamma family | 2.7.1. Inverse transformed gamma distribution | 2.7.2. Inverse gamma distribution | 2.7.3. Inverse Weibull distribution | 2.7.4. Inverse exponential | 3. Bibliography | 3.1. General books | 3.2. Books dedicated to a distribution family | 3.3. Books with applications
