plotter.NewLine() and NaN

[giancarlo]

Looking to plot multiple lines a graph. Something like the image below 

one consistent line (blue) and two other lines that cut off if they have no Y value corresponding to the X value.

currently i have something like this 

```

func makeXYs(x, y []float64) (plotter.XYs, error) {

  var XYs plotter.XYs

  if len(x) == len(y) {

    log.Debug("x and y match length. Creating X and Y points for graph")

    for i, _ := range x {

      XYs = append(XYs, plotter.XY{X: x[i], Y: y[i]})

    }

    return XYs, nil

  } else {

    return nil, fmt.Errorf("x:( %v )and y:( %v ) DON'T match length", x, y)

  }

}

```

```

dateX := []float64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

blueY := []float64{15, 13, 19,  14, 11 ,13, 12, 17, 18, 20 }

redY := []float64{21, 23, 29, NaN NaN, NaN, NaN, 24, 25 ,26}

greenY := []float64{NaN, NaN, NaN, 5, 3, 9, 4, NaN, NaN, NaN}

blueXYs, _ := makeXYs(dateX, blueY)

redXYs, _ := makeXYs(dateX, redY)

greenXYs, _ := makeXYs(dateX, greenY)

p := plot.New()

blueLine, _ := plotter.NewLine(blueXYs)

redLine, err := plotter.NewLine(redXYs)

if err != nil {

    log.Error(err)

}

greenLine, err := plotter.NewLine(greenXYs)

if err != nil {

    log.Error(err)

}

p.Add(blueXYs, redXYs, greenXYs)

```

OUTPUT:

```

ERRO[0000] plotter: NaN data point
ERRO[0000] plotter: NaN data point

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x0 pc=0x103017bf8]

goroutine 1 [running]:
gonum.org/v1/plot/plotter.(*Line).Len(0x0)
    <autogenerated>:1 +0x28
gonum.org/v1/plot/plotter.Range({0x103320d30, 0x140004d34b0})
    /Users/gespi/go/pkg/mod/gonum.org/v1/pl...@v0.11.0/plotter/plotter.go:58 +0xc8
gonum.org/v1/plot/plotter.XYRange({0x103320560, 0x0})
    /Users/gespi/go/pkg/mod/gonum.org/v1/pl...@v0.11.0/plotter/plotter.go:125 +0x5c
gonum.org/v1/plot/plotter.(*Line).DataRange(0x0)
    /Users/gespi/go/pkg/mod/gonum.org/v1/pl...@v0.11.0/plotter/line.go:144 +0x34
gonum.org/v1/plot.(*Plot).Add(0x14000265400, {0x140000a7c68, 0x3, 0x3})
    /Users/gespi/go/pkg/mod/gonum.org/v1/pl...@v0.11.0/plot.go:127 +0x17c
goblin-trader/pkg/plotty.SuperTrend(0x1400000e018, {0x1400022f800, 0x71, 0x80}, {0x1400022fc00, 0x71, 0x80})
    /Users/gespi/github/goblin-trader/pkg/plotty/supertrend.go:68 +0x6b0
goblin-trader/cmd.glob..func1(0x103b93960, {0x1400012ef60, 0x0, 0x6})
    /Users/gespi/github/goblin-trader/cmd/run.go:32 +0x158
github.com/spf13/cobra.(*Command).execute(0x103b93960, {0x1400012ef00, 0x6, 0x6})
    /Users/gespi/go/pkg/mod/github.com/spf13/co...@v1.5.0/command.go:876 +0x65c
github.com/spf13/cobra.(*Command).ExecuteC(0x103b936e0)
    /Users/gespi/go/pkg/mod/github.com/spf13/co...@v1.5.0/command.go:990 +0x410
github.com/spf13/cobra.(*Command).Execute(...)
    /Users/gespi/go/pkg/mod/github.com/spf13/co...@v1.5.0/command.go:918
goblin-trader/cmd.Execute()
    /Users/gespi/github/goblin-trader/cmd/root.go:33 +0x6c
main.main()
    /Users/gespi/github/goblin-trader/main.go:10 +0x20
exit status 2

I do not know how NaNs are supposed to be handled when plotting using plotter. I am not a data science specialist nor even a novice at it. So any help on how to produce lines that are cut off would be appreciated. I tried switching the NaNs to Zeros but they dont cut off the line and it still results in one line with the lines touching zero points. 

 

[Dan Kortschak]

On Wed, 2022-09-28 at 16:30 -0700, giancarlo wrote:
>
> I do not know how NaNs are supposed to be handled when plotting using
> plotter. I am not a data science specialist nor even a novice at it.
> So any help on how to produce lines that are cut off would be
> appreciated. I tried switching the NaNs to Zeros but they dont cut
> off the line and it still results in one line with the lines touching
> zero points. 

NaN and Inf are not allowed in sequences of floats for plotting in the
general case, and certainly not in the Line plotter.

What I would do for your data if you will be having NaN/Inf in the
inputs would be to wrap plotter.NewLine so that you take a plotter.XYs
and return a []plotter.XYs that splits the sequences when NaN/Inf
appear. These would then be handed to plotter.NewLine to get a
[]plotter.Line that you would Add to the plot.Plot as a group.

This might seem involved, but with a helper function should not be too
much of an issue.

Sebastian may have a better solution.

Dan

[giancarlo]

this is a route I have considered but not sure if this was the official way to do this. Good to hear from the community before i make some moves. TY 

Will await sebastions suggestions as well :) 

[Sebastien Binet]

On Tue Oct 4, 2022 at 00:45 CET, giancarlo wrote:
> this is a route I have considered but not sure if this was the official
> way
> to do this. Good to hear from the community before i make some moves. TY
>
> Will await sebastions suggestions as well :)

I don't have much to add.
perhaps we could export a helper to break a plotter.Line/plotter.XYs into
a set of plotters (ie: a []plotter.Line/[]plotter.XYs)

this could perhaps be generalized with the help of generics (to turn a
[]T where T implement plot.Plotter, into a plot.Plotter)


hth,
-s

>
> On Friday, September 30, 2022 at 4:44:47 PM UTC-4 Dan Kortschak wrote:
>
> > On Wed, 2022-09-28 at 16:30 -0700, giancarlo wrote:
> > >
> > > I do not know how NaNs are supposed to be handled when plotting using
> > > plotter. I am not a data science specialist nor even a novice at it.
> > > So any help on how to produce lines that are cut off would be
> > > appreciated. I tried switching the NaNs to Zeros but they dont cut
> > > off the line and it still results in one line with the lines touching
> > > zero points.
> >
> > NaN and Inf are not allowed in sequences of floats for plotting in the
> > general case, and certainly not in the Line plotter.
> >
> > What I would do for your data if you will be having NaN/Inf in the
> > inputs would be to wrap plotter.NewLine so that you take a plotter.XYs
> > and return a []plotter.XYs that splits the sequences when NaN/Inf
> > appear. These would then be handed to plotter.NewLine to get a
> > []plotter.Line that you would Add to the plot.Plot as a group.
> >
> > This might seem involved, but with a helper function should not be too
> > much of an issue.
> >
> > Sebastian may have a better solution.
> >
> > Dan
> >
> >
>

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