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Reference Guide
DynamicSlice.py File Reference

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 DynamicSlice
 

Detailed Description

View in nbviewer Open in SWAN Example of function called when a mouse event occurs in a pad.

When moving the mouse in the canvas, a second canvas shows the projection along X of the bin corresponding to the Y position of the mouse. The resulting histogram is fitted with a gaussian. A "dynamic" line shows the current bin position in Y. This more elaborated example can be used as a starting point to develop more powerful interactive applications exploiting CINT as a development engine.

Note that a class is used to hold on to the canvas that display the selected slice.

pict1_DynamicSlice.py.png
import sys
import ctypes
from ROOT import gRandom, gPad, gROOT, gVirtualX
from ROOT import kTRUE, kRed
from ROOT import TCanvas, TH2, TH2F
class DynamicExec:
def __init__( self ):
self._cX = None
self._cY = None
self._old = None
def __call__( self ):
h = gPad.GetSelected();
if not h:
return
if not isinstance( h, TH2 ):
return
gPad.GetCanvas().FeedbackMode( kTRUE )
# erase old position and draw a line at current position
px = gPad.GetEventX()
py = gPad.GetEventY()
uxmin, uxmax = gPad.GetUxmin(), gPad.GetUxmax()
uymin, uymax = gPad.GetUymin(), gPad.GetUymax()
pxmin, pxmax = gPad.XtoAbsPixel( uxmin ), gPad.XtoAbsPixel( uxmax )
pymin, pymax = gPad.YtoAbsPixel( uymin ), gPad.YtoAbsPixel( uymax )
if self._old != None:
gVirtualX.DrawLine( pxmin, self._old[1], pxmax, self._old[1] )
gVirtualX.DrawLine( self._old[0], pymin, self._old[0], pymax )
gVirtualX.DrawLine( pxmin, py, pxmax, py )
gVirtualX.DrawLine( px, pymin, px, pymax )
self._old = px, py
upx = gPad.AbsPixeltoX( px )
x = gPad.PadtoX( upx )
upy = gPad.AbsPixeltoY( py )
y = gPad.PadtoY( upy )
padsav = gPad
# create or set the display canvases
if not self._cX:
self._cX = TCanvas( 'c2', 'Projection Canvas in X', 730, 10, 700, 500 )
else:
self._DestroyPrimitive( 'X' )
if not self._cY:
self._cY = TCanvas( 'c3', 'Projection Canvas in Y', 10, 550, 700, 500 )
else:
self._DestroyPrimitive( 'Y' )
self.DrawSlice( h, y, 'Y' )
self.DrawSlice( h, x, 'X' )
padsav.cd()
def _DestroyPrimitive( self, xy ):
proj = getattr( self, '_c'+xy ).GetPrimitive( 'Projection '+xy )
if proj:
proj.IsA().Destructor( proj )
def DrawSlice( self, histo, value, xy ):
yx = xy == 'X' and 'Y' or 'X'
# draw slice corresponding to mouse position
canvas = getattr( self, '_c'+xy )
canvas.SetGrid()
canvas.cd()
bin = getattr( histo, 'Get%saxis' % xy )().FindBin( value )
hp = getattr( histo, 'Projection' + yx )( '', bin, bin )
hp.SetFillColor( 38 )
hp.SetName( 'Projection ' + xy )
hp.SetTitle( xy + 'Projection of bin=%d' % bin )
hp.Fit( 'gaus', 'ql' )
hp.GetFunction( 'gaus' ).SetLineColor( kRed )
hp.GetFunction( 'gaus' ).SetLineWidth( 6 )
canvas.Update()
if __name__ == '__main__':
# create a new canvas.
c1 = TCanvas('c1', 'Dynamic Slice Example', 10, 10, 700, 500 )
c1.SetFillColor( 42 )
c1.SetFrameFillColor( 33 )
# create a 2-d histogram, fill and draw it
hpxpy = TH2F( 'hpxpy', 'py vs px', 40, -4, 4, 40, -4, 4 )
hpxpy.SetStats( 0 )
x, y = ctypes.c_double( 0.1 ), ctypes.c_double( 0.101 )
for i in range( 50000 ):
# pass ctypes doubles by reference, then retrieve their modified values with .value
gRandom.Rannor( x, y )
hpxpy.Fill( x.value, y.value )
hpxpy.Draw( 'COL' )
# Add a TExec object to the canvas (explicit use of __main__ is for IPython)
import __main__
__main__.slicer = DynamicExec()
c1.AddExec( 'dynamic', 'TPython::Exec( "slicer()" );' )
c1.Update()
Author
Rene Brun, Johann Cohen-Tanugi, Wim Lavrijsen, Enric Tejedor

Definition in file DynamicSlice.py.