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Fix Histogram implementation.

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The former behavior of Histogram did not agree with the documentation. The documentation matched
the spirit of floats.Within, so keep the documentation and fix the behavior. This change updates
the function behavior, as well as corrects the test and the example.
This commit is contained in:
btracey
2015-01-10 10:41:15 -08:00
parent 0311b04883
commit a723bc27d8
2 changed files with 68 additions and 45 deletions
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55
stat.go
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@@ -385,7 +385,7 @@ func Hellinger(p, q []float64) float64 {
// Histogram sums up the weighted number of data points in each bin.
// The weight of data point x[i] will be placed into count[j] if
// dividers[j-1] <= x < dividers[j]. The "span" function in the floats package can assist
// dividers[j] <= x < dividers[j+1]. The "span" function in the floats package can assist
// with bin creation.
//
// The following conditions on the inputs apply:
@@ -399,37 +399,47 @@ func Histogram(count, dividers, x, weights []float64) []float64 {
panic("stat: slice length mismatch")
}
if count == nil {
count = make([]float64, len(dividers)+1)
count = make([]float64, len(dividers)-1)
}
if len(count) != len(dividers)+1 {
if len(dividers) < 2 {
panic("histogram: fewer than two dividers")
}
if len(count) != len(dividers)-1 {
panic("histogram: bin count mismatch")
}
if !sort.Float64sAreSorted(dividers) {
panic("dividers are not sorted")
panic("histogram: dividers are not sorted")
}
if !sort.Float64sAreSorted(x) {
panic("x data are not sorted")
panic("histogram: x data are not sorted")
}
if len(x) == 0 {
for i := range count {
count[i] = 0
}
return count
}
if x[0] < dividers[0] {
panic("histogram: minimum x value is less than lowest divider")
}
if x[len(x)-1] >= dividers[len(dividers)-1] {
panic("histogram: minimum x value is greater than highest divider")
}
idx := 0
comp := dividers[idx]
comp := dividers[idx+1]
if weights == nil {
for _, v := range x {
if v < comp || idx == len(count)-1 {
if v < comp {
// Still in the current bucket
count[idx]++
continue
}
// Need to find the next divider where v is less than the divider
// or to set the maximum divider if no such exists
for j := idx + 1; j < len(count); j++ {
if j == len(dividers) {
idx = len(dividers)
break
}
if v < dividers[j] {
// Find the next divider where v is less than the divider
for j := idx + 1; j < len(dividers); j++ {
if v < dividers[j+1] {
idx = j
comp = dividers[j]
comp = dividers[j+1]
break
}
}
@@ -439,21 +449,16 @@ func Histogram(count, dividers, x, weights []float64) []float64 {
}
for i, v := range x {
if v < comp || idx == len(count)-1 {
if v < comp {
// Still in the current bucket
count[idx] += weights[i]
continue
}
// Need to find the next divider where v is less than the divider
// or to set the maximum divider if no such exists
// Need to find the next divider where v is less than the divider.
for j := idx + 1; j < len(count); j++ {
if j == len(dividers) {
idx = len(dividers)
break
}
if v < dividers[j] {
if v < dividers[j+1] {
idx = j
comp = dividers[j]
comp = dividers[j+1]
break
}
}