Merge pull request #148 from scipp/monitor-norm-nansum

Mask zero values in the monitor

Author: nvaytet

src/ess/powder/conversion.py

@@ -4,7 +4,6 @@
 Coordinate transformations for powder diffraction.
 """
 
-import numpy as np
 import sciline as sl
 import scipp as sc
 import scippneutron as scn
@@ -317,8 +316,7 @@ def compute_monitor_time_of_flight(
     wf[time_of_flight.PulseStride] = pulse_stride
     wf[time_of_flight.PulseStrideOffset] = pulse_stride_offset
     out = wf.compute(time_of_flight.ResampledTofData)
-    inds = out.values == 0.0
-    out.values[inds] = np.nan
+    out.masks["zero_counts"] = out.data == sc.scalar(0.0, unit=out.data.unit)
     return TofMonitorData[RunType, MonitorType](out)