diff --git a/Project.toml b/Project.toml
index bb3d6a1f..a9236850 100644
--- a/Project.toml
+++ b/Project.toml
@@ -31,6 +31,7 @@ DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 StatsBase = "2913bbd2-ae8a-5f71-8c99-4fb6c76f3a91"
 StatsModels = "3eaba693-59b7-5ba5-a881-562e759f1c8d"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+CategoricalArrays = "324d7699-5711-5eae-9e2f-1d82baa6b597"
 
 [targets]
-test = ["Test", "CSV", "DataFrames", "StatsBase", "StatsModels"]
+test = ["Test", "CSV", "DataFrames", "StatsBase", "StatsModels", "CategoricalArrays"]
diff --git a/change.log b/change.log
index cee121f8..0512a873 100644
--- a/change.log
+++ b/change.log
@@ -1,7 +1,11 @@
+v0.9.2
+  * z matrix for random effect
+  * contain ddf
+
 v0.9.1
   * update deps
   * anova table (experimental)
-  
+
 v0.9.0
   * remove redundant code
   * change in nlopt solver keyword handling
diff --git a/src/anova.jl b/src/anova.jl
index dba323cd..a08fadb3 100644
--- a/src/anova.jl
+++ b/src/anova.jl
@@ -41,7 +41,7 @@ function anova(lmm::LMM{T}; ddf::Symbol = :satter) where T
         elseif ddf == :contain
             df[i]  = dof_contain(lmm, i)
         elseif ddf == :residual
-            df[i]  = dof_residual(lmm, i)
+            df[i]  = dof_residual(lmm)
         end
         pval[i] = ccdf(FDist(ndf[i], df[i]), F[i])
     end
diff --git a/src/dof_contain.jl b/src/dof_contain.jl
index 4915a115..00280cc2 100644
--- a/src/dof_contain.jl
+++ b/src/dof_contain.jl
@@ -15,8 +15,6 @@ function zmatrix(lmm::LMM, i)
     end
     rzm
 end
-
-
 function fullzmatrix(lmm)
     fzm = Matrix{Int}(undef, nobs(lmm), 0)
     for r = 1:length(lmm.covstr.random)