Dear all,

I am trying to convolve a RooExponential with a RooHistPdf; the time constant tau of the RooExponential is

distributed according to a RooHistPdf.

I want then to generate some data from the projected convolved distribution.

I have followed the useful example rf211_paramconv.C.

When I try to run my code (attached here together with the needed data for the tau distribution),

I get the following error:

```
[#0] ERROR:Eval -- RooAbsReal::logEvalError(tauHPDF_fft) evaluation error,
origin : RooHistPdf::tauHPDF_fft[ pdfObs=(tau_shifted_FFTBuffer2) ]
message : p.d.f normalization integral is zero or negative
server values: pdfObs=(tau_shifted_FFTBuffer2 = -1.485)
```

at this line:

```
RooDataHist* d = projtrapConv->generateBinned(t,1000) ;
```

the error gets repeated over and over.

Later on other errors appear, like:

```
[#0] ERROR:Eval -- RooAbsReal::logEvalError(trapConv_Int[tau]_Norm[t,tau]) evaluation error,
origin : RooRealIntegral::trapConv_Int[tau]_Norm[t,tau][ Int trapConv_Norm(t,tau) d[Ana](tau) ]
message : function value is NAN
server values: !sumList=(), !intList=(), !anaList=(tau = -2.51149), !jacList=(), !facList=(), !func=trapConv=0, !sumCat=()
```

Am I missing something?

I am using the following root version:

```
------------------------------------------------------------
| Welcome to ROOT 6.02/04 http://root.cern.ch |
| (c) 1995-2014, The ROOT Team |
| Built for macosx64 |
| From tag v6-02-04, 17 January 2015 |
| Try '.help', '.demo', '.license', '.credits', '.quit'/'.q' |
------------------------------------------------------------
```

Any help will be greatly appreciated!

Many thanks in advance and best regards,

Marco Bomben

tests_140224-fei4-250um-fl3.8e15-extract_traps-V400-taue-in-ns.root (3.81 KB)

convolution_hist.C (3.43 KB)