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Former Member
Aug 30, 2010 at 03:25 PM

Trendline Problems with Numeric Axis Charts


I am attempting to create a chart in Crystal Report XI that lists the time period (months) on the x-axis and the number of units sold on the y-axis. I have created the chart as a numeric axis bar chart because there are some months that do not have any units sold and converted the dates through a formula to periods where the first month requested equals 0 and each of the following months is incremented by 1. The problem I am having is that the data is displayed correctly but when I request a trendline be displayed, I am getting a trendline that does not correspond with the data. For example I have a 60 month time period where half the months are zero and the maximum number of units sold is 8 and the trend line runs from 30 at period 0 and 24 at period 60. The equation is displayed as y=-1.1x29.9 and the actual trendline should be y=0.0078x0.5802. The trendline in a side by side bar chart is closer but is skewed by the fact that periods with no units sold is not displayed but is closer than what I am getting with the numeric axis bar chart. I have also noted that if I change the scale of the x-axis from automatic or change the gap width, I get wildly different trendlines for each change that still does not match the data. I have also tried to use the date axis bar chart but again the data is presented correctly but the trendline is not correct. So my question is: Can I use a side by side bar chart, in which the trendline seems more accurate, that can account for months with no data and/or is there something that I am missing on setting up a trendline for a numeric axis chart?