RootUtils::ScatterH2 Class Reference

A 2-D histogram that can draw a proper scatter plot. More...

#include <ScatterH2.h>

Inheritance diagram for RootUtils::ScatterH2:

Collaboration diagram for RootUtils::ScatterH2:

Classes
struct	Pair
	One point. Avoid std::pair so that we don't have duplicate dicts. More...

Public Member Functions
	ScatterH2 ()
	Default constructor.
	ScatterH2 (const char *name, const char *title, Int_t nbinsx, Axis_t xlow, Axis_t xup, Int_t nbinsy, Axis_t ylow, Axis_t yup)
	Constructor.
	ScatterH2 (const char *name, const char *title, Int_t nbinsx, const Double_t *xbins, Int_t nbinsy, Axis_t ylow, Axis_t yup)
	Constructor.
	ScatterH2 (const char *name, const char *title, const TArrayD &xbins, Int_t nbinsy, Axis_t ylow, Axis_t yup)
	Constructor.
virtual void	Paint (Option_t *option="")
	Standard ROOT paint method.
virtual void	Reset (Option_t *option="")
	Standard ROOT reset method.
virtual Int_t	Fill (Axis_t x, Axis_t y, Stat_t w)
	Standard ROOT fill method.
virtual Int_t	Fill (Axis_t x, Axis_t y)
	Standard ROOT fill method.
bool	scatter () const
	Get the current value of the scatter flag.
bool	scatter (bool flag)
	Set the scatter flag.
int	shadestep () const
	Get the current value of shadestep.
int	shadestep (int shadestep)
	Set value of shadestep.
ScatterH2 *	rescale (const char *name, double xscale, double yscale) const
	Return a new plot with all data points multiplied by a constant.

Private Member Functions
virtual Int_t	Fill (Axis_t, const char *, Stat_t)
virtual Int_t	Fill (const char *, Axis_t, Stat_t)
virtual Int_t	Fill (const char *, const char *, Stat_t)
Int_t	Fill (Axis_t)
Int_t	Fill (const char *, Stat_t)
	ClassDef (RootUtils::ScatterH2, 1)

Private Attributes
bool	m_scatter
	The scatter flag.
int	m_shadestep
	shadestep option.
std::vector< Pair >	m_vals
	The collection of points that have been plotted.

Detailed Description

A 2-D histogram that can draw a proper scatter plot.

This is a variation on TH2F that can draw itself as a proper scatter plot — that is, each point really corresponds exactly to one Fill() call. (The default behavior of TH2F bins the histogram, and then dithers in random points when asked to draw a scatter plot.)

This is, in essence, a combination of TGraph2D and TH2F.

Use scatter() to control whether we plot as a real scatter plot, or if we get the default root behavior.

Note that the implementation requires saving the values of all the points. Beware if you're trying to make plots with a really huge number of points.

If scatter plotting is on, it will be drawn by putting the default polymarker at each point. Note that once the plot starts getting dense, this can hide the structure of the distribution: if all points are set, then adding a new point makes no visible difference. To help with this, shading can also be used to show the distribution density. This is controlled by the parameter shadestep.

If shadestep is zero, no shading is done, and markers are drawn with the default color.

If shadestep is greater than zero, then the color used for each pixel is ((N-1)*shadestep, 0, 0), (as (R,G,B)), where N is the number of data points plotted on the pixel.

If shadestep is less then zero, the shading is done similarly, except that the scale factor is chosen to that the densest pixel will have a R channel of 255.

Definition at line 66 of file ScatterH2.h.

Constructor & Destructor Documentation

ScatterH2() [1/4]

RootUtils::ScatterH2::ScatterH2

(

)

Default constructor.

Definition at line 34 of file ScatterH2.cxx.

  : m_scatter (true),
    m_shadestep (0)
{
}

ScatterH2() [2/4]

RootUtils::ScatterH2::ScatterH2	(	const char *	name,
		const char *	title,
		Int_t	nbinsx,
		Axis_t	xlow,
		Axis_t	xup,
		Int_t	nbinsy,
		Axis_t	ylow,
		Axis_t	yup )

Constructor.

Parameters

name	Histogram name.
title	Histogram title.
nbinsx	Number of bins on x-axis.
xlow	x-axis lower limit.
xup	x-axis upper limit.
nbinsy	Number of bins on y-axis.
ylow	y-axis lower limit.
yup	y-axis upper limit.

Definition at line 52 of file ScatterH2.cxx.

  : TH2F (name, title, nbinsx, xlow, xup, nbinsy, ylow, yup),
    m_scatter (true),
    m_shadestep (0)
{
}

ScatterH2() [3/4]

RootUtils::ScatterH2::ScatterH2	(	const char *	name,
		const char *	title,
		Int_t	nbinsx,
		const Double_t *	xbins,
		Int_t	nbinsy,
		Axis_t	ylow,
		Axis_t	yup )

Constructor.

Parameters

name	Histogram name.
title	Histogram title.
nbinsx	Number of bins on x-axis.
xbins	Array of bin boundaries.
nbinsy	Number of bins on y-axis.
ylow	y-axis lower limit.
yup	y-axis upper limit.

Definition at line 72 of file ScatterH2.cxx.

  : TH2F (name, title, nbinsx, xbins, nbinsy, ylow, yup),
    m_scatter (true),
    m_shadestep (0)
{
}

ScatterH2() [4/4]

RootUtils::ScatterH2::ScatterH2	(	const char *	name,
		const char *	title,
		const TArrayD &	xbins,
		Int_t	nbinsy,
		Axis_t	ylow,
		Axis_t	yup )

Constructor.

Parameters

name	Histogram name.
title	Histogram title.
xbins	Array of bin boundaries.
nbinsy	Number of bins on y-axis.
ylow	y-axis lower limit.
yup	y-axis upper limit.

Definition at line 92 of file ScatterH2.cxx.

  : TH2F (name, title, xbins.GetSize()-1, xbins.GetArray(),
          nbinsy, ylow, yup),
    m_scatter (true),
    m_shadestep (0)
{
}

Member Function Documentation

ClassDef()

RootUtils::ScatterH2::ClassDef ( RootUtils::ScatterH2 , 1  )

private

Fill() [1/7]

Int_t RootUtils::ScatterH2::Fill ( Axis_t x, Axis_t y )

virtual

Standard ROOT fill method.

Parameters

x	x-coordinate.
y	y-coordinate.

Definition at line 288 of file ScatterH2.cxx.

{
  return Fill (x, y, 1.0);
}

Fill() [2/7]

Int_t RootUtils::ScatterH2::Fill ( Axis_t x, Axis_t y, Stat_t w )

virtual

Standard ROOT fill method.

Parameters

x	x-coordinate.
y	y-coordinate.
w	Weight.

This overrides the TH2 Fill method. The data point is saved in our list.

Definition at line 275 of file ScatterH2.cxx.

{
  // Remember the point in m_vals.
  m_vals.push_back (Pair (x, y));
  return TH2F::Fill (x, y, w);
}

Fill() [3/7]

Int_t RootUtils::ScatterH2::Fill ( Axis_t )

inlineprivate

Definition at line 249 of file ScatterH2.h.

{return -1;}

Fill() [4/7]

virtual Int_t RootUtils::ScatterH2::Fill ( Axis_t , const char * , Stat_t  )

inlineprivatevirtual

Definition at line 246 of file ScatterH2.h.

{ return -1; }

Fill() [5/7]

virtual Int_t RootUtils::ScatterH2::Fill ( const char * , Axis_t , Stat_t  )

inlineprivatevirtual

Definition at line 247 of file ScatterH2.h.

{ return -1; }

Fill() [6/7]

virtual Int_t RootUtils::ScatterH2::Fill ( const char * , const char * , Stat_t  )

inlineprivatevirtual

Definition at line 248 of file ScatterH2.h.

{ return -1; }

Fill() [7/7]

Int_t RootUtils::ScatterH2::Fill ( const char * , Stat_t  )

inlineprivate

Definition at line 250 of file ScatterH2.h.

{return -1;}

Paint()

void RootUtils::ScatterH2::Paint ( Option_t * option = "" )

virtual

Standard ROOT paint method.

Parameters

option

Paint options. See TH2.

This overrides the TH2 Paint method. It suppresses the normal histogram plot if scatter mode is on.

Definition at line 110 of file ScatterH2.cxx.

{
  if (!m_scatter) {
    TH2F::Paint (option);
    return;
  }
 
  // Muck with things to prevent the normal histogram output.
  double oldmax = GetMaximumStored ();
  double oldmin = GetMinimumStored ();
  SetMaximum (0);
  SetMinimum (0);
 
  // Get the frame, etc., drawn.
  TH2F::Paint (option);
 
  SetMaximum (oldmax);
  SetMinimum (oldmin);
 
  // Gotta to this to get the coordinates set up properly.
  gPad->Update();
 
  // Work around a root bug.
  // THistPainter::PaintTable2 will add a TPaveStats object
  // to the function list.  However, if we then try to paint
  // the same histo again, then there is code in THistPainter
  // that expects the things in the function list to derive
  // from TF1.  There's no checking on the downcast, so root
  // crashes...
  GetListOfFunctions()->Clear();
 
  // Get coordinate bounds.
  Double_t u, v;
  Double_t umin = gPad->GetUxmin();
  Double_t umax = gPad->GetUxmax();
  Double_t vmin = gPad->GetUymin();
  Double_t vmax = gPad->GetUymax();
 
  int pxmin = gPad->XtoAbsPixel (umin);
  int pxmax = gPad->XtoAbsPixel (umax);
  int pymin = gPad->YtoAbsPixel (vmin);
  int pymax = gPad->YtoAbsPixel (vmax);
  if (pxmin > pxmax) std::swap (pxmin, pxmax);
  if (pymin > pymax) std::swap (pymin, pymax);
  int pxsize = pxmax - pxmin + 1;
  int pysize = pymax - pymin + 1;
  std::vector<unsigned int> counts (pxsize * pysize);
 
  TVirtualPad* pad = gPad;
 
  // Count the number of points on each pixel.
  unsigned int maxcount = 0;
  unsigned int n = m_vals.size();
  for (unsigned int i=0; i<n; i++) {
    u = pad->XtoPad (m_vals[i].first);
    v = pad->YtoPad (m_vals[i].second);
    if (u < umin) u = umin;
    if (u > umax) u = umax;
    if (v < vmin) v = vmin;
    if (v > vmax) v = vmax;
 
    int px = pad->XtoAbsPixel (u);
    int py = pad->YtoAbsPixel (v);
    if (px < pxmin || px > pxmax || py < pymin || py > pymax) continue;
    unsigned ndx = (px-pxmin) + (py-pymin) * pxsize;
    assert (ndx < counts.size());
    ++counts[ndx];
    if (counts[ndx] > maxcount)
      maxcount = counts[ndx];
  }
 
  const unsigned int NCOLOR = 255;
 
  // Figure out shading.
  float step = 0;
  if (m_shadestep) {
    if (m_shadestep > 0)
      step = m_shadestep;
    else if (maxcount > 2)
      step = static_cast<float>(NCOLOR-1)/(maxcount-1);
    else
      step = NCOLOR-1;
  }
 
  // Count the number of points for each color.
  unsigned int ccounts[NCOLOR];
  std::uninitialized_fill (ccounts, ccounts+NCOLOR, 0);
  size_t ndxmax = counts.size();
  for (unsigned int i=0; i < ndxmax; i++) {
    unsigned int count = counts[i];
    if (count > 0) {
      unsigned int color = static_cast<unsigned int> ((count-1)*step);
      if (color >= NCOLOR) color = NCOLOR-1;
      ++ccounts[color];
    }
  }
 
  TPolyMarker* pms[NCOLOR];
  std::uninitialized_fill (pms, pms+NCOLOR, (TPolyMarker*)0);
 
  // Fill in the polymarkers.
  for (int py = pymin; py <= pymax; ++py) {
    for (int px = pxmin; px <= pxmax; ++px) {
      unsigned int ndx = (px-pxmin) + (py-pymin) * pxsize;
      assert (ndx < ndxmax);
      unsigned int count = counts[ndx];
      if (count > 0) {
        Double_t u = pad->AbsPixeltoX (px);
        Double_t v = pad->AbsPixeltoY (py);
        unsigned int color = static_cast<unsigned int> ((count-1)*step);
        if (color >= NCOLOR) color = NCOLOR-1;
 
        TPolyMarker* pm = pms[color];
        if (!pm) {
          pm = new TPolyMarker (ccounts[color]);
          ccounts[color] = 0;
          pm->SetMarkerStyle (GetMarkerStyle());
          pm->SetMarkerSize (GetMarkerSize());
          if (color != 0)
            pm->SetMarkerColor (TColor::GetColor (color, 0, 0));
          pms[color] = pm;
        }
        pm->SetPoint (ccounts[color]++, u, v);
      }
    }
  }
 
  // Draw the points.
  for (unsigned int i = 0; i < NCOLOR; i++) {
    if (pms[i]) {
      pms[i]->Paint();
      delete pms[i];
    }
  }
}

rescale()

ScatterH2 * RootUtils::ScatterH2::rescale	(	const char *	name,
		double	xscale,
		double	yscale ) const

Return a new plot with all data points multiplied by a constant.

Parameters

name	Name for the new plot.
xscale	x-axis scale factor.
yscale	y-axis scale factor.

Definition at line 357 of file ScatterH2.cxx.

{
  int nx = GetXaxis()->GetNbins();
  double xlo = GetXaxis()->GetXmin();
  double xhi = GetXaxis()->GetXmax();
 
  int ny = GetYaxis()->GetNbins();
  double ylo = GetYaxis()->GetXmin();
  double yhi = GetYaxis()->GetXmax();
 
#if 0
  ScatterH2* hnew = new ScatterH2 (name, GetTitle(),
                                   nx, xscale*xlo, xscale*xhi,
                                   ny, yscale*ylo, yscale*yhi);
#endif
  ScatterH2* hnew = dynamic_cast<ScatterH2*> (this->Clone (name));
  if (hnew == 0)
    return 0;
  hnew->GetXaxis()->Set (nx, xscale*xlo, xscale*xhi);
  hnew->GetYaxis()->Set (ny, yscale*ylo, yscale*yhi);
  size_t n = hnew->m_vals.size();
  for (size_t i = 0; i < n; i++) {
    hnew->m_vals[i].first *= xscale;
    hnew->m_vals[i].second *= yscale;
  }
 
  return hnew;
}

Reset()

void RootUtils::ScatterH2::Reset ( Option_t * option = "" )

virtual

Standard ROOT reset method.

Parameters

option

Reset options. See TH2.

This overrides the TH2 Reset method. We may need to clear the saved points, too.

Definition at line 254 of file ScatterH2.cxx.

{
  TString opt = option;
  if (!opt.Contains("ICE")) {
    // Clear out m_vals too, releasing memory.
    std::vector<Pair> tmp;
    m_vals.swap (tmp);
  }
  TH2F::Reset (option);
}

scatter() [1/2]

bool RootUtils::ScatterH2::scatter

(

)

const

Get the current value of the scatter flag.

If it's true, then this histogram will draw as a real scatter plot. Otherwise, the default root behavior is used.

Definition at line 300 of file ScatterH2.cxx.

{
  return m_scatter;
}

scatter() [2/2]

bool RootUtils::ScatterH2::scatter

(

bool

flag

)

Set the scatter flag.

Parameters

flag	The new value of the scatter flag.

Returns

The previous value of the scatter flag.

If it's true, then this histogram will draw as a real scatter plot. Otherwise, the default root behavior is used.

Definition at line 314 of file ScatterH2.cxx.

{
  bool x = m_scatter;
  m_scatter = flag;
  return x;
}

shadestep() [1/2]

int RootUtils::ScatterH2::shadestep

(

)

const

Get the current value of shadestep.

If zero, no shading is done. If greater than zero, pixel brightness is increased by this much for each additional data point. If less than zero, pixel brightness is scaled so that pixels with the most data points have a brightness of 255.

Definition at line 331 of file ScatterH2.cxx.

{
  return m_shadestep;
}

shadestep() [2/2]

int RootUtils::ScatterH2::shadestep

(

int

shadestep

)

Set value of shadestep.

Parameters

shadestep

The new value for shadestep.

Returns

The previous value of shadestep.

If zero, no shading is done. If greater than zero, pixel brightness is increased by this much for each additional data point. If less than zero, pixel brightness is scaled so that pixels with the most data points have a brightness of 255.

Definition at line 348 of file ScatterH2.cxx.

{
  int x = m_shadestep;
  m_shadestep = shadestep;
  return x;
}

Member Data Documentation

m_scatter

bool RootUtils::ScatterH2::m_scatter

private

The scatter flag.

If true, plot as a scatter plot.

Definition at line 219 of file ScatterH2.h.

m_shadestep

int RootUtils::ScatterH2::m_shadestep

private

shadestep option.

If zero, no shading is done. If greater than zero, pixel brightness is increased by this much for each additional data point. If less than zero, pixel brightness is scaled so that pixels with the most data points have a brightness of 255.

Definition at line 228 of file ScatterH2.h.

m_vals

std::vector<Pair> RootUtils::ScatterH2::m_vals

private

The collection of points that have been plotted.

Definition at line 240 of file ScatterH2.h.

---

The documentation for this class was generated from the following files:

• ScatterH2.h
• ScatterH2.cxx