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package stats
// Outliers holds mild and extreme outliers found in data
type Outliers struct {
Mild Float64Data
Extreme Float64Data
}
// QuartileOutliers finds the mild and extreme outliers
func QuartileOutliers(input Float64Data) (Outliers, error) {
if input.Len() == 0 {
return Outliers{}, EmptyInputErr
}
// Start by sorting a copy of the slice
copy := sortedCopy(input)
// Calculate the quartiles and interquartile range
qs, _ := Quartile(copy)
iqr, _ := InterQuartileRange(copy)
// Calculate the lower and upper inner and outer fences
lif := qs.Q1 - (1.5 * iqr)
uif := qs.Q3 + (1.5 * iqr)
lof := qs.Q1 - (3 * iqr)
uof := qs.Q3 + (3 * iqr)
// Find the data points that are outside of the
// inner and upper fences and add them to mild
// and extreme outlier slices
var mild Float64Data
var extreme Float64Data
for _, v := range copy {
if v < lof || v > uof {
extreme = append(extreme, v)
} else if v < lif || v > uif {
mild = append(mild, v)
}
}
// Wrap them into our struct
return Outliers{mild, extreme}, nil
}
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