Lines' intersection

[#1]

Hello,

I would like to know if it is possible to highlight (maybe just add a label) the lines' intersection and draw special lines to the X and Y axes like I did in Paint.

[marcus_sommer]

This could be possible but I think it won't be easy. The intersection-point could be a line with Xi - Yi with a condition to be visible only if the diff-value = 0. Your red-lines will be probably more difficult - you could try something similar like my suggestion for the intersection point and/or with a presentation-line from tab presentation (bottom right) and/or the trend-lines from tab expressions (bottom left) could be used.

Another (additional) approach might be to use several charts which lay over eachother (with appropriate adjustments to the layout) and/or the use from background-picture with visibility-conditions.

A further possibility could be an extension - maybe there are an existing one or one which could be adjusted to this.

- Marcus

[swuehl]

I guess you don't know the point of intersection, nor the equation of the lines, but you are having two sets of x/ y values that define the lines or can be used for fitting lines, right?

So you would first need to calculate / determine the equations of the two lines (i.e. slope and y-axis intersection) using linest_m() and linest_b() functions in QV.

If you've got the equations (slope and intersection values), calculate the point of intersection.

Line–line intersection - Wikipedia, the free encyclopedia

If you've got the point, you can use the coordinates to draw reference lines, additional expression lines or symbols in your chart.