Intercepts on a 2D graph

[Frank Siebert]

Good morning,

I have just started using Autograph and am a few days into the trial version.

I have come across a problem I cannot find a solution for.

On a 2D graph I have plotted a number of random points (scatterplot) on a simple x-y graph. I then used Autograph to plot the Best Fit Line.

What I am now trying to achieve is to show a number of dashed or dotted intercept lines (in different colours) that go vertically from selected values on the x-axis then on meeting the Best Fit Line travel horizontally to show the corresponding values on the y-axis.

The solution to the above is probably fairly simple and obvious but for the life of me I cannot find how to do this.

I have spent many hours searching on how to accomplish this but failed miserably!

Any help with a solution would be highly appreciated.

Thanks in advance.

Frank Siebert

[Support]

Dear Frank,

Here are a couple of ways:

1. In Point Mode add a point to the line of best fit. Select the point, right-click and add horizontal and vertical lines through this point.

This is very quick but obviously the lines don't stop at the axes and the point the controls the position of the lines is on the line of best fit rather than the x-axis.

2. Plot y = 0 and in Point Mode add a point to this line (the x-axis).
Select the point and create a vertical line.
In Point Mode hold down the Ctrl key and click on the intersection of this vertical line and the line of best fit.
Select this intersection point, right-click and choose horizontal line.
Plot x = 0.
In Point Mode hold down the Ctrl key and click on the intersection of the horizontal line and x = 0 (the y-axis).
Now we have three points and lots of lines.
Hide all the lines except the line of best fit by selecting them and right-click > hide object.
Add line segments between the point on the x-axis and the point on the line of best fit, and another between the point on the line of best fit and the y-axis.

This second method provides you want you want visually but obvious requires a few more steps.

Best regards,

Simon

[Frank Siebert]

Dear Simon,

Solution 2 was perfect!

Many thanks for your very quick response to my query and also your excellent and detailed instructions.

I try and sort out problems myself, usually after looking at all resources available i.e. program help, forum, tutorials etc but this one had me really scatching my head.

I will almost certainly purchase once I have completed the trial.

Thanks again for the help, very much appreciated.

Kind regards,

Frank.

[Support]

Dear Frank,

No problem, I am glad you found it useful. Definitely one worth asking on the forums, I don't think there are any specific instructions written down for this particular problem anywhere. You will notice this form of construction where you hide some objects which are there just for "scaffolding" is quite useful in a number of situations.

Best regards,

Simon

(21-06-2012 04:16 PM)Frank Siebert Wrote:  Dear Simon,

Solution 2 was perfect!

Many thanks for your very quick response to my query and also your excellent and detailed instructions.

I try and sort out problems myself, usually after looking at all resources available i.e. program help, forum, tutorials etc but this one had me really scatching my head.

I will almost certainly purchase once I have completed the trial.

Thanks again for the help, very much appreciated.

Kind regards,

Frank.