# User function abd NumConv function at RooFit

Happy New Year all,
To the my previous question there is new one

ex-myNumConv.C (24.7 KB)
Now there are 2 problems -

1. plot of the input data is very strange - histogram reproduce
data - 4-th gpad, but function in RooFit has strange shape for
2. I started to use RooNumConvPdf for simple input function -
myf3() - BW and gauss() - this time convolution works
(unlike of FFT method) BUT very strange also -
at the plot - gpad 1 and 3 - there is drop of points at t=4.6 - 5.6
What does it mean !? where is the problem ?
thanks,

root -l
-> .L ex-myNumConv.C
-> Convolution(); >& l.l
.> …

Hi @babintsev,

Happy New Year! I am inviting @moneta to this thread as he may be able to help with this.

Cheers,
J.

Dear Lorenzo,
I am trying to use RooFit methods to get convoluted crosssection
of neutron resonancies. Results:

1. FFT method does not work for me I do not know why
2. try NumConvPdf - strange result !
• I use ex-myNumConv.C : read input data file : data-1-10.txt
(in fact I read full data: but it is too big, so use short variant)

• I draw 4 wimdows:
w-1: data simulation using convolution fxg - you can see
a lot of missing regions
w-2: draw data-function which I used for convolution ->
(in other words - it is data, which I read)
you see that plot shows values ONLY in the region 3-5 eV
–> compare this with full data sample at the w-4 !

w-3: here I draw result of convolution :
BLUE - initial BW resonance (the same as at w-2)
RED - result of numeric convolution : cut at E= 4.6 eV !

so, questions : is it problem with plot procedure !?
OR is it problem with RooFit methods ?
OR it is my error --> where and what ?!

`````` 2 topics are here :
1) w-2 and w-4 :  why plot does not reproduce input data ?
2) I use simple variant:
take BW resonance and gauss - as it is from examples
at Internet
- w-1  data sample using this convolution (fxg)
- w-3  convolution  fxg - you see cuts in region
(it is the same problem, when I use my input data)
``````

thank you,

ex-myNumConv.C (24.7 KB) data-1-10.txt (5.8 KB)

Thank you Vladmir for the explanations. I will have a look, but it will take me same time, since it is not an easy answer.
Is this then a duplicate of RooFit import histogram plot ?

Cheers

Lorenzo

… thank you, there are some modifications from
previous one : I worked with my own data,
and the last picture : using simple BW and Gauss
as a part of the question…