github.com/go-graphite/carbonapi@v0.17.0/expr/functions/sigmoid/function.go (about)

     1  package sigmoid
     2  
     3  import (
     4  	"context"
     5  	"math"
     6  
     7  	"github.com/go-graphite/carbonapi/expr/helper"
     8  	"github.com/go-graphite/carbonapi/expr/interfaces"
     9  	"github.com/go-graphite/carbonapi/expr/types"
    10  	"github.com/go-graphite/carbonapi/pkg/parser"
    11  )
    12  
    13  type sigmoid struct{}
    14  
    15  func GetOrder() interfaces.Order {
    16  	return interfaces.Any
    17  }
    18  
    19  func New(_ string) []interfaces.FunctionMetadata {
    20  	res := make([]interfaces.FunctionMetadata, 0)
    21  	f := &sigmoid{}
    22  	functions := []string{"sigmoid"}
    23  	for _, n := range functions {
    24  		res = append(res, interfaces.FunctionMetadata{Name: n, F: f})
    25  	}
    26  	return res
    27  }
    28  
    29  // sigmoid(seriesList)
    30  func (f *sigmoid) Do(ctx context.Context, eval interfaces.Evaluator, e parser.Expr, from, until int64, values map[parser.MetricRequest][]*types.MetricData) ([]*types.MetricData, error) {
    31  	arg, err := helper.GetSeriesArg(ctx, eval, e.Arg(0), from, until, values)
    32  	if err != nil {
    33  		return nil, err
    34  	}
    35  	var results []*types.MetricData
    36  
    37  	for _, a := range arg {
    38  		r := a.CopyLink()
    39  		r.Name = "sigmoid(" + a.Name + ")"
    40  		r.Values = make([]float64, len(a.Values))
    41  		r.Tags["sigmoid"] = "sigmoid"
    42  
    43  		for i, v := range a.Values {
    44  			if math.IsNaN(v) || math.Exp(-v) == -1 { // check for -1 result as this would cause a divide by zero error
    45  				r.Values[i] = math.NaN()
    46  			} else {
    47  				r.Values[i] = (1 / (1 + math.Exp(-v)))
    48  			}
    49  		}
    50  		results = append(results, r)
    51  	}
    52  	return results, nil
    53  }
    54  
    55  // Description is auto-generated description, based on output of https://github.com/graphite-project/graphite-web
    56  func (f *sigmoid) Description() map[string]types.FunctionDescription {
    57  	return map[string]types.FunctionDescription{
    58  		"sigmoid": {
    59  			Description: "Takes one metric or a wildcard seriesList and applies the sigmoid function 1 / (1 + exp(-x)) to each datapoint.\n\nExample:\n\n.. code-block:: none\n\n  &target=sigmoid(Server.instance01.threads.busy)\n  &target=sigmoid(Server.instance*.threads.busy)",
    60  			Function:    "sigmoid(seriesList)",
    61  			Group:       "Transform",
    62  			Module:      "graphite.render.functions",
    63  			Name:        "sigmoid",
    64  			Params: []types.FunctionParam{
    65  				{
    66  					Name:     "seriesList",
    67  					Required: true,
    68  					Type:     types.SeriesList,
    69  				},
    70  			},
    71  		},
    72  	}
    73  }