Update docs, add midlife function (#6)

* Update docs, add midlife function

* add tests for midlife

* fix formatting

Project.toml

@@ -1,7 +1,7 @@
 name = "PersistenceDiagramsBase"
 uuid = "b1ad91c1-539c-4ace-90bd-ea06abc420fa"
 authors = ["mtsch <matijacufar@gmail.com>"]
-version = "0.1.0"
+version = "0.1.1"
 
 [deps]
 Compat = "34da2185-b29b-5c13-b0c7-acf172513d20"

src/PersistenceDiagramsBase.jl

@@ -8,6 +8,7 @@ export PersistenceDiagram,
     birth,
     death,
     persistence,
+    midlife,
     dim,
     threshold,
     birth_simplex,

src/diagrams.jl

@@ -1,12 +1,13 @@
 """
-    PersistenceDiagram{P<:PersistenceInterval} <: AbstractVector{P}
+    PersistenceDiagram <: AbstractVector{PersistenceInterval}
 
 Type for representing persistence diagrams. Behaves exactly like a vector of
-`PersistenceInterval`s, but is can have metadata attached to it and supports pretty printing
-and plotting.
+`PersistenceInterval`s, but can have additional metadata attached to it. It supports pretty
+printing and plotting.
 
 Can be used as a table with any function that uses the
-[`Tables.jl`](https://github.com/JuliaData/Tables.jl) interface.
+[`Tables.jl`](https://github.com/JuliaData/Tables.jl) interface. Note that using it as a
+table will only keep interval endpoints and the `dim` and `threshold` attributes.
 
 # Example
 

src/intervals.jl

@@ -1,9 +1,9 @@
 """
     PersistenceInterval
 
-The type that represents a persistence interval. It behaves exactly like a `Tuple{Float64,
-Float64}`, but can have meta data attached to it. The metadata is accessible
-with `getproperty`.
+Type for representing persistence intervals. It behaves exactly like a `Tuple{Float64,
+Float64}`, but can have meta data attached to it. The metadata is accessible with
+`getproperty` or the dot syntax.
 
 # Example
 
@@ -63,6 +63,13 @@ Get the persistence of `interval`, which is equal to `death - birth`.
 """
 persistence(int::PersistenceInterval) = death(int) - birth(int)
 
+"""
+    midlife(interval)
+
+Get the midlife of the `interval`, which is equal to `(birth + death) / 2`.
+"""
+midlife(int::PersistenceInterval) = (birth(int) + death(int)) / 2
+
 Base.isfinite(int::PersistenceInterval) = isfinite(death(int))
 
 ###

test/diagrams.jl

@@ -36,6 +36,8 @@ using Test
         @test !isfinite(int2)
         @test persistence(int1) == 1
         @test persistence(int2) == Inf
+        @test midlife(int1) == 1.5
+        @test midlife(int2) == Inf
 
         @test eltype(int1) ≡ Float64
         @test eltype(PersistenceInterval) ≡ Float64