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function.go
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function.go
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package ifft
import (
"context"
"fmt"
"math/cmplx"
"github.com/bookingcom/carbonapi/expr/helper"
"github.com/bookingcom/carbonapi/expr/interfaces"
"github.com/bookingcom/carbonapi/expr/types"
"github.com/bookingcom/carbonapi/pkg/parser"
realFFT "github.com/mjibson/go-dsp/fft"
)
type ifft struct {
interfaces.FunctionBase
}
func GetOrder() interfaces.Order {
return interfaces.Any
}
func New(configFile string) []interfaces.FunctionMetadata {
res := make([]interfaces.FunctionMetadata, 0)
f := &ifft{}
functions := []string{"ifft"}
for _, n := range functions {
res = append(res, interfaces.FunctionMetadata{Name: n, F: f})
}
return res
}
// ifft(absSeriesList, phaseSeriesList)
func (f *ifft) Do(ctx context.Context, e parser.Expr, from, until int32, values map[parser.MetricRequest][]*types.MetricData, getTargetData interfaces.GetTargetData) ([]*types.MetricData, error) {
absSeriesList, err := helper.GetSeriesArg(ctx, e.Args()[0], from, until, values, getTargetData)
if err != nil {
return nil, err
}
var phaseSeriesList []*types.MetricData
if len(e.Args()) > 1 {
phaseSeriesList, err = helper.GetSeriesArg(ctx, e.Args()[1], from, until, values, getTargetData)
if err != nil {
return nil, err
}
}
var results []*types.MetricData
for j, a := range absSeriesList {
r := *a
r.Values = make([]float64, len(a.Values))
r.IsAbsent = make([]bool, len(a.Values))
if len(phaseSeriesList) > j {
p := phaseSeriesList[j]
name := fmt.Sprintf("ifft(%s, %s)", a.Name, p.Name)
r.Name = name
values := make([]complex128, len(a.Values))
for i, v := range a.Values {
if a.IsAbsent[i] {
v = 0
}
values[i] = cmplx.Rect(v, p.Values[i])
}
values = realFFT.IFFT(values)
for i, v := range values {
r.Values[i] = cmplx.Abs(v)
}
} else {
name := fmt.Sprintf("ifft(%s)", a.Name)
r.Name = name
values := realFFT.IFFTReal(a.Values)
for i, v := range values {
r.Values[i] = cmplx.Abs(v)
}
}
results = append(results, &r)
}
return results, nil
}
// Description is auto-generated description, based on output of https://github.com/graphite-project/graphite-web
func (f *ifft) Description() map[string]types.FunctionDescription {
return map[string]types.FunctionDescription{
"ifft": {
Description: "An algorithm that samples a signal over a period of time (or space) and divides it into its frequency components. Computes discrete Fourier transform https://en.wikipedia.org/wiki/Fast_Fourier_transform \n\nExample:\n\n.. code-block:: none\n\n &target=fft(server*.requests_per_second)\n\n &target=fft(server*.requests_per_second, \"abs\")\n",
Function: "ifft(seriesList, phaseSeriesList)",
Group: "Transform",
Module: "graphite.render.functions.custom",
Name: "ifft",
Params: []types.FunctionParam{
{
Name: "seriesList",
Required: true,
Type: types.SeriesList,
},
{
Name: "phaseSeriesList",
Required: true,
Type: types.SeriesList,
},
},
},
}
}