func sampleFormat(p *profile.Profile, sampleIndex string, mean bool) (value, meanDiv sampleValueFunc, v *profile.ValueType, err error) {
	if len(p.SampleType) == 0 {
		return nil, nil, nil, fmt.Errorf("profile has no samples")
	}
	index, err := p.SampleIndexByName(sampleIndex)
	if err != nil {
		return nil, nil, nil, err
	}
	value = valueExtractor(index)
	if mean {
		meanDiv = valueExtractor(0)
	}
	v = p.SampleType[index]
	return

// total will only include samples with that label.
func computeTotal(prof *profile.Profile, value, meanDiv func(v []int64) int64) int64 {
	var div, total, diffDiv, diffTotal int64
	for _, sample := range prof.Sample {
		var d, v int64
		v = value(sample.Value)
		if meanDiv != nil {
			d = meanDiv(sample.Value)
		}
		if v < 0 {
			v = -v
		}
		total += v
		div += d