Hi Michael, Valeri, Selemon, As I quickly realized that it might take more time to process the mails than to implement the code, I have implemented this function in my development version. Comments are welcome. Rene Brun TH1 *TH1::Project3D(Option_t *option) { // Project a 3-d histogram into 1 or 2-d histograms depending on the // option parameter // option may contain a combination of the characters x,y,z,e // option = "x" return the x projection into a TH1D histogram // option = "y" return the y projection into a TH1D histogram // option = "z" return the z projection into a TH1D histogram // option = "xy" return the x versus y projection into a TH2D histogram // option = "yx" return the y versus x projection into a TH2D histogram // option = "xz" return the x versus z projection into a TH2D histogram // option = "zx" return the z versus x projection into a TH2D histogram // option = "yz" return the y versus z projection into a TH2D histogram // option = "zy" return the z versus y projection into a TH2D histogram // // if option contains the string "e", errors are computed // // The projection is made for the selected bins only Michael A. Lisa wrote: > > Hello Rene, > > Yes, but a TNtuple will get too big, if a lot of data points > are collected. With a histogram, the binning reduces memory usage. > > So TNtuple would be more powerful in principle, but is unpractical > when dealing with large amounts of data. > So a question would be: are there plans to implement this > projection feature of 3D histograms? > > Thanks, > Mike Lisa > > +-------------------------------------------------------------------+ > | Mike Lisa | email: lisa@mps.ohio-state.edu | > | Department of Physics | | > | 2156 Smith Laboratory | Van de Graaff <--- usually here | > | Ohio State University | ph: (614) 292-4775 / fax: 292-4833 | > | 174 West 18th Avenue | | > | Columbus, OH 43210 | http://vdgus1.mps.ohio-state.edu/~lisa/ | > +-------------------------------------------------------------------+ > > On Thu, 29 Jul 1999, Rene Brun wrote: > > > Hi Valeri, > > Your request could be implemented. To be complete, one has to consider > > all possible combinations, including 1-d projections. > > > > I did not put much effort in this area, as I believe that is is more > > general > > and powerful to define a small TNtuple object with x,y,z from which you > > can > > already make all kinds of projections 1-d, 2-d and 3-d including > > selections. > > > > Rene Brun > > > > > > Valeri Fine (Faine) wrote: > > > > > > ----- Original Message ----- > > > From: Selemon Bekele <bekele@pacific.mps.ohio-state.edu> > > > To: STAR software <starsofi-l@bnl.gov> > > > Sent: 29 èþëÿ 1999 ã. 10:38 > > > Subject: projecting a histogram > > > > > > > > > > > > > > > I have a three dimensional histogram which I want to project to a certain > > > > axis. Is there a way how to do it in root4star? I cheked the root class > > > > library and found in a class which relates to one dimensional histograms a > > > > method which projects only to the third axis which it calls Z. It would be > > > > nice if two more methods could be added so that one can project also onto > > > > the other two axes separately. For the time being, a way around this problem > > > > is to fill three histograms where each component is passed as a third > > > > argument: > > > > > > > > Fill(x,y,z),Fill(z,x,y),Fill(y,z,x) > > > > > > > > and do the projection. > > > > ******************************************* > > > > > > > > Selemon Bekele > > > > e-mail bekele@pacific.mps.ohio-state.edu > > > > Tel. (614)294-4863 (home) > > > > > > > > ******************************************* > > > > > > > > > > > > > > > > > >
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