not really sure i understand your question.
for each day you get values A, B and C ... you store them in index (one document with 3 fields).
now you want to display vertical bar chart showing you these values on per day basis ? so just for today for example ? or do you want to show it over the course of days ? (like time histogram)
if you are interested in just todays data, you can select TODAY in the timepicker in the top right corner. if you are interested n any other dates .... just select appropriate ranges
start with adding date histogram to the x axis, choose interval to be day. this requires that you are storing date with your records.
then change the default count metric to the average of field A.
add two more metrics: average of field B and average of field C.
now the bars will be stacked at this point. go to options tab and for bar mode choose grouped.
this should be it.