auto rdfb = ROOT::RDF::FromSqlite("http://root.cern/files/root_download_stats.sqlite", "SELECT * FROM accesslog;");

auto minTimeStr = *rdfb.Reduce([](std::string a, std::string b) {return std::min(a, b);}, "Time", std::string("Z"));

std::cout << "Minimum time is '" << minTimeStr << "'" << std::endl;

double minTime = TDatime(minTimeStr.c_str()).Convert();
double now = TDatime().Convert();

auto rdf = rdfb.Define("datime", [](const std::string &time){return TDatime(time.c_str()).Convert();}, {"Time"});

auto h614 = rdf.Filter([](const std::string &v){ return 0 == v.find("6.14");}, {"Version"})
               .Histo1D({"h614", "Download time for version 6.14", 16, minTime, now}, {"datime"});

auto h616 = rdf.Filter([](const std::string &v){ return 0 == v.find("6.16");}, {"Version"})
               .Histo1D({"h616", "Download time for version 6.16", 16, minTime, now}, {"datime"});

auto h618 = rdf.Filter([](const std::string &v){ return 0 == v.find("6.18");}, {"Version"})
               .Histo1D({"h618", "Download time for version 6.18", 16, minTime, now}, {"datime"});

auto histoList = {h614, h616, h618};
auto canvases = new std::vector<TCanvas*>(histoList.size());

gStyle->SetTimeOffset(0);
gStyle->SetOptStat(0);
auto histoIdx = 0U;
for (auto histo : histoList) {
   canvases->at(histoIdx) = new TCanvas();
   histo->GetXaxis()->LabelsOption("v");
   histo->GetXaxis()->SetTimeDisplay(1);
   histo->GetXaxis()->SetLabelSize(0.02);
   histo->GetXaxis()->SetNdivisions(512, kFALSE);
   histo->GetXaxis()->SetTimeFormat("%Y-%m-%d");
   histo->DrawClone();
   histoIdx++;
}

%jsroot on
gROOT->GetListOfCanvases()->Draw()