diff --git a/src/CoordVisualize.jl b/src/CoordVisualize.jl
index 73ecc03..e0a8927 100644
--- a/src/CoordVisualize.jl
+++ b/src/CoordVisualize.jl
@@ -4,5 +4,6 @@ using Dates
 
 include("typedef.jl")
 include("parser.jl")
+include("edit.jl")
 
-end # end module CoordVisualize
+end # module CoordVisualize
diff --git a/src/edit.jl b/src/edit.jl
new file mode 100644
index 0000000..a9ac869
--- /dev/null
+++ b/src/edit.jl
@@ -0,0 +1,26 @@
+"""
+    split_log(log::CoordLog, at::Unsigned, notes_1::AbstractString, notes_2::AbstractString)::Vector{CoordLog}
+
+Split `log` at `at`, i.e. to `1:at` and `at:end` then assign `notes_1` and `notes_2` to notes for each other.
+"""
+function split_log(log::CoordLog, at::Unsigned, notes_1::AbstractString, notes_2::AbstractString)::Vector{CoordLog}
+    @assert at < size(log.coords)[1] "Split index must be less than original log length($(size(log.coords)[1]))"
+    [
+        CoordLog(log.coords[1:at, :], log.logdate, notes_1),
+        CoordLog(log.coords[at:end, :], log.logdate, notes_2),
+    ]
+end
+
+function split_log(log::CoordLog, at::Integer, notes_1::AbstractString, notes_2::AbstractString)::Vector{CoordLog}
+    split_log(log, UInt(at), notes_1, notes_2)
+end
+
+
+"""
+    assign_note!(log::CoordLog, new_note::AbstractString)
+
+Replace `note` in `log` with `new_note`.
+"""
+function assign_note!(log::CoordLog, new_note::AbstractString)
+    log.note = new_note
+end
diff --git a/src/typedef.jl b/src/typedef.jl
index b8ea29f..7f722ba 100644
--- a/src/typedef.jl
+++ b/src/typedef.jl
@@ -1,7 +1,15 @@
 using Dates
-struct CoordLog{T <: AbstractFloat}
+mutable struct CoordLog{T <: AbstractFloat}
     coords::Matrix{T}
     logdate::DateTime
     note::String
 end
 
+"""
+    n_coords(log::CoordLog)::Integer
+
+Get number of coordinates in `log`.
+"""
+function n_coords(log::CoordLog)::Integer
+    size(log.coords)[1]
+end