After constructive comments from Egil Arnesen in Tromsø, Norway and searching in various textbooks I have decided that for v2 the following two definitions will be implemented:
histogram: A graph, where there is one bar for each value present in the data. The height of the bar corresponds to the count of records in the data. (possibly later the percentage of data). Each bar starts at the x-value which was in the data (e.g. age 45 is shown from 45-46.) And the width of one bar is the same as the unit of the x variable. The X-axis is numerical and can be scaled with minimum, maximum and increase.E.g. from 25 to 100 with tickmarks by 5 (25 30 35 ......95 100)
Bar: A graph, where there is one bar for each value represented in the data. The X-axis is categorical and the bar is centered around the tick mark, which would show the value label (or the value) given by the x value.
If anyone has comments to this please send to this list.
The principle of the histogram will be implemented also for EpiCurve (but has not been done yet). The mentioned implementation of bar and histogram should work from build 112 uploaded shortly before this mail. (Minor problem with the build 112 uploaded yesterday).
Kind regards
Jens Lauritsen EpiData Association