Hi Peter, if I'm setting a y-axis to log scale with min limit of -1000 and max limit of 1000, Chartdirector only displays 0.1, 1, 10, 100, 1000, but if i set it from -1000 to 0, it would display -1000, -100, -10, -1, -0.1. Why is it that a log scale can't display negative to positive axis?
Would you mind to clarify what do you expect to see if the log scale is from 1000 to -1000?
The log scale is like 1000, 100, 10, 1, 0.1, 0.01, 0.001, 0.0001, 0.00001, .... No matter how long you extend the scale, it can never reach zero. In maths, log(x) tends to negative infinitely when x tends to 0, and log(0) is undefined. That's why you cannot extend a positive log scale to 0 or negative, and vice versa. If the scale can include 0, then it is not a log scale.
and it can never reach the positive side. The distance between -1 and 1 is infinite or undefined. That why a log scale cannot have both positive and negative values.
For your case, if the positive and negative points do not connect together (that is, there is no line joining a positive point with a negative point), you can consider your chart to consist of two data sets for the positive and negative points, and they use two different log axes - one is from -1000 to -1, and the other from 1 to 1000. The distance between -1 to 1 is undefined, and for your case you can set to any distance you want.
The following is a method to use two different axis but make it looks like a single axis.
(a) In ChartDirector, by default, the height of the y-axis will be equal to the height of the plot area. It is possible to add "margins" to the y-axis so that the axis only occupies part of the plot area border. The following is an example that the y-axis is shortened at the top-end to leave space for the legend box.