Topic: Bug report: y=kx+m with a very big k and a very small m

First of all, yes, I am aware that I can use relationships or parametic functions to create vertical lines. I was basically testing how close it was possible to get by using standard functions.

I defined two constants, "inf" and "xpos". xpos = 8, and inf = 2900000 (2.9*10^6).

I created a standard function as: "y=inf*x-inf*xpos".

As I changed the value of inf to something even bigger, I noticed that sometimes the function wasn't visible at all. Zooming out or in made the function appear sometimes, but it disappeared again later. I created an animation of the graph using Calc -> Animate, Constant: inf, Range: From: 2900000, To: 3500000, Step: 10000. I noticed that in the animation, the graph was sometimes visible and sometimes not. Couldn't figure out why.

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Attachment icon y_kx+m.grf 1.14 kb, 425 downloads since 2010-03-17 

Re: Bug report: y=kx+m with a very big k and a very small m

When Draw type for the function is Automatic Graph does some guessing, which usually improves the quality of the plotting. When the function seems very steep, Graph tries to determine if the function really is steep or if there is a whole in the function. It looks like your function is hitting the limit for where Graph can guess correctly.

If you change Draw type to Lines Graph will stop guessing and just connect all points on the function, which is what you want.