added distance per stroke metric

rowers/dataprep.py

@@ -1567,6 +1567,9 @@ def dataprep(rowdatadf,id=0,bands=True,barchart=True,otwpower=True,
             drivenergy = drivelength*averageforce
         
     distance = rowdatadf.ix[:,'cum_dist']
+    velo = 500./p
+
+    distanceperstroke = 60.*velo/spm
 
     
     data = DataFrame(
@@ -1588,6 +1591,7 @@ def dataprep(rowdatadf,id=0,bands=True,barchart=True,otwpower=True,
 	    distance=distance,
 	    drivespeed=drivespeed,
             rhythm=rhythm,
+            distanceperstroke=distanceperstroke,
 	    )
 	)
 
@@ -1667,6 +1671,7 @@ def dataprep(rowdatadf,id=0,bands=True,barchart=True,otwpower=True,
 
         velo = 500./p
 
+
         ergpw = 2.8*velo**3
         efficiency = 100.*ergpw/power