[Paraview] extract location of minimum
Eelco van Vliet
eelcovv at gmail.com
Fri Mar 4 11:10:36 EST 2011
Hi David,
Many thanks for you suggestions. I was away for a while but had some time to
look at this points this week again. The using the Python calculator brought
me on the trail of using The Programmable Pythonscript filter.
My quest: I want to extrate the minimum value and its position for a time
series of VTK files and write the data for all the time step to one single
file.
With the advice so for, I now have the following construction.
First I read a series of VTK files representating the velocity over a cross
section
*U_pxy_z0_600_t0 = LegacyVTKReader( FileNames=[ List of filename ])*
Then I extract the U_z velocity component
*Calculator2 = Calculator()
Calculator2.AttributeMode = 'point_data'
Calculator2.Function = 'U_Z'
Calculator2.ResultArrayName = 'U_Z'
*Then I create a Programmable Filter
ProgrammableFilter2 = ProgrammableFilter()
ProgrammableFilter2.RequestUpdateExtentScript = ''
ProgrammableFilter2.PythonPath = ''
ProgrammableFilter2.RequestInformationScript = ''
ProgrammableFilter2.OutputDataSetType = 'vtkTable'
ProgrammableFilter2.Script = 'blabla'
For the script of the Programmable filter, I am now doing the following
input=inputs[0]
Uzdata= input.PointData['U_Z']
numPoints = input.GetNumberOfPoints()
uzmin=Uzdata[0]
for i in range(numPoints):
uz=Uzdata[i]
if uz<uzmin:
minpos=input.GetPoint(i)
uzmin=uz
print "uzmin: ",uzmin,min(Uzdata)
print "minpos: ",minpos
output.RowData.append(uzmin, 'uzmin')
*
*At this point I am stuck. First of all, the minpos variable is a tuple, and
I don't know how to apend this to the output.RowData, because it needs to be
and vtkArray. What is the way to convert a tuple into a vtkArray?
Second of all: if I step over the time step and see correctly the minpos and
uzmin value updated in the spreadsheet viewer. However, how can I collect
all the values into one array and then write to a single file ? Or should I
just write the data of each time step to a seperate file ?
Hopefully someone can give me some advice on how to approach this issue.
Many thanks in advance!
Regards,
Eelco
On Fri, Feb 11, 2011 at 10:28 PM, David E DeMarle
<dave.demarle at kitware.com>wrote:
> I suggest replacing the Calculator and DescriptiveStatistics filters
> with one python programmable filter (or python calculator if you are
> using 3.10). That way the data type isn't changed and Fetch will do
> what you expect it to - produce a standard vtkDataSet with 1
> point/cell.
>
> The python calculator expression to get an average x,y,and Z point location
> is:
> hstack([
> [global_mean(inputs[0].Points[:,0])],
> [global_mean(inputs[0].Points[:,1])],
> [global_mean(inputs[0].Points[:,2])]
> ])
>
> If you then Fetch it's output and get the min (or equivalently max or
> just deliver the whole thing and just look at any of the points) you
> will get the average X Y and Z coordinates in a 3 component array
> names Result.
>
> David E DeMarle
> Kitware, Inc.
> R&D Engineer
> 28 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-371-3971 x109
>
>
>
> On Fri, Feb 11, 2011 at 10:34 AM, Eelco van Vliet <eelcovv at gmail.com>
> wrote:
> > Hi David,
> >
> > Thanks for you suggestion, I got much closer to what I want, but not
> quite
> > yet. I have the feeling I need one slight extra hint :)
> >
> > To obtain the position of a minimun value I now do the script below: I
> get
> > the mimimum value first with MinMax, then I Threshold the original data
> on a
> > range between min and 0.9*min (the minimum values are negative), then I
> use
> > the calculator to get the x and y position of this range, and then I use
> the
> > DescriptiveStatitics filter to get the average mean of the position. I
> can
> > even use Fetch again to obtain the data, but now the very last step: how
> to
> > I get the mean data itself ? Sorry, I just don't understand how that
> > data.objects exactly work, and there is not much assessible documentation
> on
> > it.
> >
> > I hope you can give me one last hint
> >
> > Regards
> >
> > Eelco
> >
> > mm=MinMax(Uzcomponent)
> > mm.Operation="MIN"
> > mindata=sm.Fetch(Uzcomponent,mm,mm)
> > mindata.GetPointData().GetNumberOfArrays()
> > a0 = mindata.GetPointData().GetArray(1)
> > uzname=a0.GetName()
> > uzmin=a0.GetTuple1(0)
> > print "minimum of %s found: %g\n "%(uzname,uzmin)
> >
> > Threshold1 = Threshold(Uzcomponent)
> > Threshold1.Scalars=['POINTS',uzname]
> > Threshold1.ThresholdRange=[uzmin,0.9*uzmin]
> >
> > CalcPos = Calculator()
> > CalcPos.AttributeMode = 'point_data'
> > CalcPos.Function = 'iHat*coordsX+jHat*coordsY+kHat*coordsZ'
> > CalcPos.ResultArrayName = 'MinPos'
> >
> > DescriptiveStatistics1 = DescriptiveStatistics()
> > DescriptiveStatistics1.VariablesofInterest = ['MinPos']
> > statistics=sm.Fetch(DescriptiveStatistics1)
> >
> >
> >
> >
> > On Thu, Feb 10, 2011 at 7:00 PM, David E DeMarle <
> dave.demarle at kitware.com>
> > wrote:
> >>
> >> The min max filter unfortunately doesn't keep track of which tuple and
> >> processor it found the min in so you can't get back to the particular
> >> point or cell it came from.
> >>
> >> Instead of using fetch and minmax, try using a values selection. Set
> >> the value to be that minimum value. Once you extract the selection and
> >> fetch it to the client, you get a copy of the actuall cell(s)/point(s)
> >> that have the minimum value and you can query them directly for their
> >> spatial location.
> >>
> >> David E DeMarle
> >> Kitware, Inc.
> >> R&D Engineer
> >> 28 Corporate Drive
> >> Clifton Park, NY 12065-8662
> >> Phone: 518-371-3971 x109
> >>
> >>
> >>
> >> On Thu, Feb 10, 2011 at 12:13 PM, Eelco van Vliet <eelcovv at gmail.com>
> >> wrote:
> >> > Dear Paraviewers,
> >> >
> >> > I would like to extract the location of a minimum value from a data
> set
> >> > in
> >> > pvbatch
> >> >
> >> > I were able to find the value of the minimum with
> >> >
> >> >
> >> >
> >> >
> >> > mm=MinMax(Uzcomponent)
> >> > mm.Operation="MIN"
> >> > mindata=sm.Fetch(Uzcomponent,mm,mm)
> >> > mindata.GetPointData().GetNumberOfArrays()
> >> > a0 = mindata.GetPointData().GetArray(1)
> >> > a1 = mindata.GetScalar()
> >> > print "name 1: ", a0.GetName()
> >> > print "tuple1: ", a0.GetTuple1(0)
> >> >
> >> > Here, a0.GetTyple1 give me the value of the minimum
> >> >
> >> > However: How do I find the location of this value ?
> >> >
> >> > Any hint appriciate!
> >> >
> >> > Regards
> >> >
> >> > Eelco
> >> >
> >> >
> >> > _______________________________________________
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> >> >
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> >
> >
>
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