Custom statistics modulde, describe program

1 files changed, 62 insertions, 0 deletions

diff --git a/src/dslr_stat.py b/src/dslr_stat.py
new file mode 100644
index 0000000..91ad744
--- /dev/null
+++ b/src/dslr_stat.py
@@ -0,0 +1,62 @@
+import math
+
+
+def _none_if_null_len(func):
+    def tmp(xs, *args, **kwargs):
+        if len(xs) == 0:
+            return None
+        return func(xs, *args, **kwargs)
+    return tmp
+
+
+@_none_if_null_len
+def mean(xs):
+    return sum(xs) / len(xs)
+
+@_none_if_null_len
+def std(xs):
+    xs_mean = mean(xs)
+    return math.sqrt(sum(
+        [(x - xs_mean) ** 2 for x in xs]) / (len(xs) - 1))
+
+@_none_if_null_len
+def _pick(xs, compar):
+    m = xs[0]
+    for t in xs[1:]:
+        if compar(t, m):
+            m = t
+    return m
+
+def min(xs):
+    return _pick(xs, lambda x, y: x < y)
+
+def max(xs):
+    return _pick(xs, lambda x, y: x > y)
+
+def _qsort(xs):
+    if len(xs) < 2:
+        return xs
+    xs = list(xs)
+    pivot = xs[0]
+    body = xs[1:]
+    return (_qsort([x for x in body if x < pivot])
+            + [pivot]
+            + _qsort([x for x in body if x >= pivot]))
+
+def _need_sorted(func):
+    return lambda xs, *args, **kwargs: func(_qsort(xs), *args, **kwargs)
+
+@_none_if_null_len
+@_need_sorted
+def q25(xs):
+    return xs[len(xs) // 4]
+
+@_none_if_null_len
+@_need_sorted
+def median(xs):
+    return xs[len(xs) // 2 ]
+
+@_none_if_null_len
+@_need_sorted
+def q75(xs):
+    return xs[3 * (len(xs) // 4)]