# A counter counts occurrences of things
# Use this instead of a `HashMap[E, Int]`
-class Counter[E: Object]
+#
+# ~~~
+# var c = new Counter[String].from(["a", "a", "b", "b", "b", "c"])
+# assert c["a"] == 2
+# assert c["b"] == 3
+# assert c["c"] == 1
+# assert c["d"] == 0
+# ~~~
+#
+# The counter class can also be used to gather statistical informations.
+#
+# ~~~~
+# assert c.length == 3 # because 3 distinct values
+# assert c.max == "b" # because "b" has the most count (3)
+# assert c.avg == 2.0 # because it is the mean of the counts
+# ~~~~
+class Counter[E]
super Map[E, Int]
# Total number of counted occurrences
- var total: Int = 0
+ #
+ # ~~~
+ # var c = new Counter[String]
+ # assert c.sum == 0
+ # c.inc_all(["a", "a", "b", "b", "b", "c"])
+ # assert c.sum == 6
+ # ~~~
+ var sum: Int = 0
private var map = new HashMap[E, Int]
+ redef fun iterator do return map.iterator
+
# The number of counted occurrences of `e`
redef fun [](e: E): Int
do
redef fun []=(e: E, value: Int)
do
- total -= self[e]
+ sum -= self[e]
self.map[e] = value
- total += value
+ sum += value
end
redef fun keys do return map.keys
redef fun values do return map.values
+ redef fun length do return map.length
+
+ redef fun is_empty do return map.is_empty
+
+ redef fun clear do
+ sum = 0
+ map.clear
+ end
+
# Count one more occurrence of `e`
fun inc(e: E)
do
self.map[e] = self[e] + 1
- total += 1
+ sum += 1
+ end
+
+ # Count one more for each element of `es`
+ fun inc_all(es: Collection[E])
+ do
+ for e in es do inc(e)
+ end
+
+ # A new Counter initialized with `inc_all`.
+ init from(es: Collection[E])
+ do
+ inc_all(es)
end
# Return an array of elements sorted by occurrences
+ #
+ # ~~~
+ # var c = new Counter[String].from(["a", "a", "b", "b", "b", "c"])
+ # assert c.sort == ["c", "a", "b"]
+ # ~~~
fun sort: Array[E]
do
var res = map.keys.to_a
- var sorter = new CounterSorter[E](self)
+ var sorter = new CounterComparator[E](self)
sorter.sort(res)
return res
end
# @toimplement by default just call `to_s` on the element
protected fun element_to_s(e: E): String
do
- do return e.to_s
+ return e.to_s
end
# Display statistical information
if list.is_empty then return
print " minimum value: {self[list.first]}"
print " maximum value: {self[list.last]}"
- print " total value: {self.total}"
- print " average value: {div(self.total,list.length)}"
+ print " total value: {self.sum}"
+ print " average value: {div(self.sum,list.length)}"
print " distribution:"
var count = 0
var sum = 0
var limit = self[list.first]
for t in list do
if self[t] > limit then
- print " <={limit}: sub-population={count} ({div(count*100,list.length)}%); cumulated value={sum} ({div(sum*100,self.total)}%)"
+ print " <={limit}: sub-population={count} ({div(count*100,list.length)}%); cumulated value={sum} ({div(sum*100,self.sum)}%)"
count = 0
sum = 0
while self[t] > limit do
count += 1
sum += self[t]
end
- print " <={limit}: sub-population={count} ({div(count*100,list.length)}%); cumulated value={sum} ({div(sum*100,self.total)}%)"
+ print " <={limit}: sub-population={count} ({div(count*100,list.length)}%); cumulated value={sum} ({div(sum*100,self.sum)}%)"
end
# Display up to `count` most used elements and `count` least used elements
if list.length <= count*2 then min = list.length
for i in [0..min[ do
var t = list[list.length-i-1]
- print " {element_to_s(t)}: {self[t]} ({div(self[t]*100,self.total)}%)"
+ print " {element_to_s(t)}: {self[t]} ({div(self[t]*100,self.sum)}%)"
end
if list.length <= count*2 then return
print " ..."
for i in [0..min[ do
var t = list[min-i-1]
- print " {element_to_s(t)}: {self[t]} ({div(self[t]*100,self.total)}%)"
+ print " {element_to_s(t)}: {self[t]} ({div(self[t]*100,self.sum)}%)"
+ end
+ end
+
+ # Return the element with the highest value (aka. the mode)
+ #
+ # ~~~
+ # var c = new Counter[String].from(["a", "a", "b", "b", "b", "c"])
+ # assert c.max == "b"
+ # ~~~
+ #
+ # If more than one max exists, the first one is returned.
+ fun max: nullable E do
+ var max: nullable Int = null
+ var elem: nullable E = null
+ for e in map.keys do
+ var v = map[e]
+ if max == null or v > max then
+ max = v
+ elem = e
+ end
+ end
+ return elem
+ end
+
+ # Return the couple with the lowest value
+ #
+ # ~~~
+ # var c = new Counter[String].from(["a", "a", "b", "b", "b", "c"])
+ # assert c.min == "c"
+ # ~~~
+ #
+ # If more than one min exists, the first one is returned.
+ fun min: nullable E do
+ var min: nullable Int = null
+ var elem: nullable E = null
+ for e in map.keys do
+ var v = map[e]
+ if min == null or v < min then
+ min = v
+ elem = e
+ end
+ end
+ return elem
+ end
+
+ # Values average (aka. arithmetic mean)
+ #
+ # ~~~
+ # var c = new Counter[String].from(["a", "a", "b", "b", "b", "c"])
+ # assert c.avg == 2.0
+ # ~~~
+ fun avg: Float do
+ if values.is_empty then return 0.0
+ return (sum / values.length).to_f
+ end
+
+ # The standard derivation of the counter values
+ #
+ # ~~~
+ # var c = new Counter[String].from(["a", "a", "b", "b", "b", "c"])
+ # assert c.std_dev > 0.81
+ # assert c.std_dev < 0.82
+ # ~~~
+ fun std_dev: Float do
+ var avg = self.avg
+ var sum = 0.0
+ for value in map.values do
+ sum += (value.to_f - avg).pow(2.0)
end
+ return (sum / map.length.to_f).sqrt
end
end
-private class CounterSorter[E: Object]
- super AbstractSorter[E]
+private class CounterComparator[E]
+ super Comparator
+ redef type COMPARED: E
var counter: Counter[E]
redef fun compare(a,b) do return self.counter.map[a] <=> self.counter.map[b]
end
private fun show_counter(c: Counter[Int])
do
var list = c.sort
- (new ComparableSorter[Int]).sort(list)
+ default_comparator.sort(list)
for e in list do
- print " {e} -> {c[e]} times ({div(c[e]*100, c.total)}%)"
+ print " {e} -> {c[e]} times ({div(c[e]*100, c.sum)}%)"
end
end
nitlanguage / nit.git / blobdiff