1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
|
package stats
import (
"math"
)
// Percentile finds the relative standing in a slice of floats
func Percentile(input Float64Data, percent float64) (percentile float64, err error) {
length := input.Len()
if length == 0 {
return math.NaN(), EmptyInputErr
}
if length == 1 {
return input[0], nil
}
if percent <= 0 || percent > 100 {
return math.NaN(), BoundsErr
}
// Start by sorting a copy of the slice
c := sortedCopy(input)
// Multiply percent by length of input
index := (percent / 100) * float64(len(c))
// Check if the index is a whole number
if index == float64(int64(index)) {
// Convert float to int
i := int(index)
// Find the value at the index
percentile = c[i-1]
} else if index > 1 {
// Convert float to int via truncation
i := int(index)
// Find the average of the index and following values
percentile, _ = Mean(Float64Data{c[i-1], c[i]})
} else {
return math.NaN(), BoundsErr
}
return percentile, nil
}
// PercentileNearestRank finds the relative standing in a slice of floats using the Nearest Rank method
func PercentileNearestRank(input Float64Data, percent float64) (percentile float64, err error) {
// Find the length of items in the slice
il := input.Len()
// Return an error for empty slices
if il == 0 {
return math.NaN(), EmptyInputErr
}
// Return error for less than 0 or greater than 100 percentages
if percent < 0 || percent > 100 {
return math.NaN(), BoundsErr
}
// Start by sorting a copy of the slice
c := sortedCopy(input)
// Return the last item
if percent == 100.0 {
return c[il-1], nil
}
// Find ordinal ranking
or := int(math.Ceil(float64(il) * percent / 100))
// Return the item that is in the place of the ordinal rank
if or == 0 {
return c[0], nil
}
return c[or-1], nil
}
|
