Change tofmin to be at the lowest event's tof

Since histogramming is inclusive on the lower bound, there is need
to shift the lower boundary to the left. The effect of the current
implementation is that when the smallest TOF is <1, the workspace
histogram started at negative values which makes a mess for log
(re)binning.

Author: peterfpeterson

Framework/DataHandling/src/LoadEventNexus.cpp

@@ -1271,8 +1271,8 @@ void LoadEventNexus::loadEvents(API::Progress *const prog, const bool monitors)
   if (eventsLoaded > 0) {
     int nBins = getProperty("NumberOfBins");
     auto binEdgesVec = std::vector<double>(nBins + 1);
-    binEdgesVec[0] = shortest_tof - 1;
-    binEdgesVec[nBins] = longest_tof + 1;
+    binEdgesVec[0] = shortest_tof;        // left edge is inclusive
+    binEdgesVec[nBins] = longest_tof + 1; // right edge is exclusive
     double binStep = (binEdgesVec[nBins] - binEdgesVec[0]) / nBins;
     for (int binIndex = 1; binIndex < nBins; binIndex++) {
       binEdgesVec[binIndex] = binEdgesVec[0] + (binStep * binIndex);

docs/source/release/v6.11.0/Framework/Algorithms/Bugfixes/37815.rst

@@ -0,0 +1 @@
+- Modify :ref:`LoadEventNexus <algm-LoadEventNexus>` so the minimum histogram bin edge is equal to the lowest time-of-flight event rather than one less. The effect is that there is no longer negative bin edges unless there is actually a negative time-of-flight in the data.