Update docstrings

Author: cmcaine

base/reduce.jl

@@ -828,7 +828,7 @@ When `domain` is omitted, `f` must have an implicit domain. In particular, if
 (domain) to values (codomain), i.e. `findmin(itr)` returns the minimal element
 of the collection `itr` and its index.
 
-Values are compared with `isgreater`.
+`NaN` is treated as less than all other values except `missing`.
 
 # Examples
 
@@ -913,7 +913,7 @@ When `domain` is omitted, `f` must have an implicit domain. In particular, if
 (domain) to values (codomain), i.e. `argmin(itr)` returns the index of the
 minimal element in `itr`.
 
-Values are compared with `isgreater`.
+`NaN` is treated as less than all other values except `missing`.
 
 # Examples
 ```jldoctest

base/reducedim.jl

@@ -967,7 +967,7 @@ end
 
 Find the minimum of `A` and the corresponding linear index along singleton
 dimensions of `rval` and `rind`, and store the results in `rval` and `rind`.
-`NaN` is treated as less than all other values.
+`NaN` is treated as less than all other values except `missing`.
 """
 function findmin!(rval::AbstractArray, rind::AbstractArray, A::AbstractArray;
                   init::Bool=true)
@@ -978,7 +978,7 @@ end
     findmin(A; dims) -> (minval, index)
 
 For an array input, returns the value and index of the minimum over the given dimensions.
-`NaN` is treated as less than all other values.
+`NaN` is treated as less than all other values except `missing`.
 
 # Examples
 ```jldoctest
@@ -1014,7 +1014,7 @@ end
 
 Find the maximum of `A` and the corresponding linear index along singleton
 dimensions of `rval` and `rind`, and store the results in `rval` and `rind`.
-`NaN` is treated as greater than all other values.
+`NaN` is treated as greater than all other values except `missing`.
 """
 function findmax!(rval::AbstractArray, rind::AbstractArray, A::AbstractArray;
                   init::Bool=true)
@@ -1025,7 +1025,7 @@ end
     findmax(A; dims) -> (maxval, index)
 
 For an array input, returns the value and index of the maximum over the given dimensions.
-`NaN` is treated as greater than all other values.
+`NaN` is treated as greater than all other values except `missing`.
 
 # Examples
 ```jldoctest
@@ -1062,7 +1062,7 @@ reducedim1(R, A) = length(axes1(R)) == 1
     argmin(A; dims) -> indices
 
 For an array input, return the indices of the minimum elements over the given dimensions.
-`NaN` is treated as less than all other values.
+`NaN` is treated as less than all other values except `missing`.
 
 # Examples
 ```jldoctest
@@ -1087,7 +1087,7 @@ argmin(A::AbstractArray; dims=:) = findmin(A; dims=dims)[2]
     argmax(A; dims) -> indices
 
 For an array input, return the indices of the maximum elements over the given dimensions.
-`NaN` is treated as greater than all other values.
+`NaN` is treated as greater than all other values except `missing`.
 
 # Examples
 ```jldoctest