Problem with TSpectrum: GetPositionX()

[Wile_E_Coyote]

You didn’t say which ROOT version you are using.

See:

Run a function in ROOT GUI

BTW. TSpectrum::Search uses a const TH1 *hin parameter so it should accept both float and double. For some examples how one can simultaneously deal with TSpectrum in ROOT 5 and TSpectrum in ROOT 6, see: