bug fix in startarg gamma

lbbe-software · Jul 29, 2024 · 60ab142 · 60ab142
1 parent 61bb19c
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Showing 5 changed files with 19 additions and 6 deletions.
diff --git a/DESCRIPTION b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: fitdistrplus
 Title: Help to Fit of a Parametric Distribution to Non-Censored or Censored Data
-Version: 1.2-1
+Version: 1.2-2
 Authors@R: c(person("Marie-Laure", "Delignette-Muller", role = "aut", email = "[email protected]", comment = c(ORCID = "0000-0001-5453-3994")),
              person("Christophe", "Dutang", role = "aut", email = "[email protected]", comment = c(ORCID = "0000-0001-6732-1501")),
              person("Regis", "Pouillot", role = "ctb"),

diff --git a/NEWS.md b/NEWS.md
@@ -1,3 +1,9 @@
+# fitdistrplus 1.2-2
+
+BUG FIX
+
+- the default starting value for the gamma distribution was wrongly computed for the rate parameter.
+
 # fitdistrplus 1.2-1
 
 NEW FEATURES

diff --git a/R/util-startarg.R b/R/util-startarg.R
@@ -481,7 +481,7 @@ startarg_transgamma_family <- function(x, distr)
     if(v > 0)
     {
       alphahat <- m^2/v
-      thetahat <- m/v
+      thetahat <- v/m
     }else #exponential case
     {
       alphahat <- 1 

diff --git a/tests/t-startingvalues-trgamma-family.R b/tests/t-startingvalues-trgamma-family.R
@@ -20,6 +20,12 @@ fitdist(x, "weibull")
 fitdist(x, "exp")
 
 
+x <- rgamma(n, 2, 2)
+
+fitdistrplus:::startarg_transgamma_family(x, "gamma")
+
+
+
 #weird examples
 x <- rep(1, n)
 

diff --git a/vignettes/starting-values.Rmd b/vignettes/starting-values.Rmd
@@ -752,7 +752,7 @@ n/\tau + \alpha\sum_i \log(x_i/\theta)
 +\sum_i \tau \frac{x_i}{\theta^2}(x_i/\theta)^{\tau-1}
 \end{pmatrix}.
 $$
-We compute moment-estimator as in gamma
+We compute the moment-estimator as in gamma \eqref{eq:gamma:relation}
 $$
 \hat\alpha = m_2^2/\mu_2, 
 \hat\theta= \mu_2/m_1.
@@ -766,11 +766,12 @@ $$
 
 Transformed gamma with $\tau=1$
 
-We compute moment-estimator as in gamma
-$$
+We compute the moment-estimator given by
+\begin{equation}
 \hat\alpha = m_2^2/\mu_2, 
 \hat\theta= \mu_2/m_1.
-$$
+\label{eq:gamma:relation}
+\end{equation}
 
 
 ### Weibull distribution