enforce naming consistency for TDist

src/univariate/continuous/tdist.jl

@@ -1,8 +1,10 @@
 immutable TDist <: ContinuousUnivariateDistribution
-    df::Float64
-    function TDist(d::Real)
-    	d > zero(d) || error("TDist: df must be positive")
-        @compat new(Float64(d))
+    ν::Float64
+
+    function TDist(ν::Real)
+    	ν > zero(ν) ||
+            throw(ArgumentError("TDist: ν must be positive."))
+        @compat new(Float64(ν))
     end
 end
 
@@ -11,49 +13,49 @@ end
 
 #### Parameters
 
-dof(d::TDist) = d.df
-params(d::TDist) = (d.df,)
+dof(d::TDist) = d.ν
+params(d::TDist) = (d.ν,)
 
 
 #### Statistics
 
-mean(d::TDist) = d.df > 1.0 ? 0.0 : NaN
+mean(d::TDist) = d.ν > 1.0 ? 0.0 : NaN
 median(d::TDist) = 0.0
 mode(d::TDist) = 0.0
 
 function var(d::TDist)
-    df = d.df
-    df > 2.0 ? df / (df - 2.0) :
-    df > 1.0 ? Inf : NaN
+    ν = d.ν
+    ν > 2.0 ? ν / (ν - 2.0) :
+    ν > 1.0 ? Inf : NaN
 end
 
-skewness(d::TDist) = d.df > 3.0 ? 0.0 : NaN
+skewness(d::TDist) = d.ν > 3.0 ? 0.0 : NaN
 
 function kurtosis(d::TDist)
-    df = d.df
-    df > 4.0 ? 6.0 / (df - 4.0) :
-    df > 2.0 ? Inf : NaN
+    ν = d.ν
+    ν > 4.0 ? 6.0 / (ν - 4.0) :
+    ν > 2.0 ? Inf : NaN
 end
 
 function entropy(d::TDist)
-    hdf = 0.5 * d.df
-    hdfph = hdf + 0.5
-    hdfph * (digamma(hdfph) - digamma(hdf)) + 0.5 * log(d.df) + lbeta(hdf,0.5)
+    h = 0.5 * d.ν
+    h1 = h + 0.5
+    h1 * (digamma(h1) - digamma(h)) + 0.5 * log(d.ν) + lbeta(h, 0.5)
 end
 
 
 #### Evaluation & Sampling
 
-@_delegate_statsfuns TDist tdist df
+@_delegate_statsfuns TDist tdist ν
 
-rand(d::TDist) = StatsFuns.Rmath.tdistrand(d.df)
+rand(d::TDist) = StatsFuns.Rmath.tdistrand(d.ν)
 
 function cf(d::TDist, t::Real)
     t == 0 && return complex(1.0)
-    h = d.df/2
-    q = d.df/4
+    h = d.ν * 0.5
+    q = d.ν * 0.25
     t2 = t*t
-    complex(2*(q*t2)^q*besselk(h,sqrt(d.df)*abs(t))/gamma(h))
+    complex(2*(q*t2)^q*besselk(h,sqrt(d.ν)*abs(t))/gamma(h))
 end
 
-gradlogpdf(d::TDist, x::Float64) = -((d.df + 1.0) * x) / (x^2 + d.df)
+gradlogpdf(d::TDist, x::Float64) = -((d.ν + 1.0) * x) / (x^2 + d.ν)