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Plot display problems when changing IP address?

The following senario has happened to me a couple of times when using Sage to demonstrate things in a classroom.

  1. I'm working on a worksheet containing plots of simple functions for a calculus class in my office. The worksheet is on a notebook server somewhere (on campus, at sagenb.org, etc..).

  2. I close my laptop, walk downstairs to class, open my laptop and plug into the projector. The laptop is now on a different wireless network, but still connects to the sage notebook server just fine. I get a red "searching for sage server" notice for just a second and then it disappears and the worksheet behaves like normal.

  3. I'm half way through class, showing plots of this and that, and I decide that I want to change the bounds on one of my plots. Say I have

    f(x) = 3x^4+4x^3-6*x^2 plot( f, (x,-2,3) )

and I want to zoom in and look at

plot( f, (x, -1, 1) )

and a new plot shows up, but it's not quite right. Sometimes I've had the experience that the plot doesn't change at all, I get the same plot as before (i.e. after editing the cell and hitting shift+enter again). Sometimes I get a new plot, but it's not correct. For example, this happened today and I got a new plot which was on the interval (-2, 1) not (-1, 1). I keep editing the cell and trying to re-evaluate the plot and get just continue to get incorrect domains or unchanged plots.

It seems like something is going on with cached images, or old images being re-displayed.

I finally figured out that I can solve the problem by cutting and pasting the code into a new cell, changing the name of the function to something different like h(x), and evaluating the cell.

Any thoughts on why this is happening or how I can prevent it from happening in the middle of class? Do I need to completely log out / log in to the server every time my IP address changes? Or maybe this problem is completely unrelated to the network change.

Plot display problems when changing IP address?

The following senario has happened to me a couple of times when using Sage to demonstrate things in a classroom.

  1. I'm working on a worksheet containing plots of simple functions for a calculus class in my office. The worksheet is on a notebook server somewhere (on campus, at sagenb.org, etc..).

  2. I close my laptop, walk downstairs to class, open my laptop and plug into the projector. The laptop is now on a different wireless network, but still connects to the sage notebook server just fine. I get a red "searching for sage server" notice for just a second and then it disappears and the worksheet behaves like normal.

  3. I'm half way through class, showing plots of this and that, and I decide that I want to change the bounds on one of my plots.

Say I have

f(x) = 3x^4+4x^3-6*x^2
3*x^4+4*x^3-6*x^2
plot( f, (x,-2,3) )

)

and I want to zoom in and look at

plot( f, (x, -1, 1) )

and a new plot shows up, but it's not quite right. Sometimes I've had the experience that the plot doesn't change at all, I get the same plot as before (i.e. after editing the cell and hitting shift+enter again). Sometimes I get a new plot, but it's not correct. For example, this happened today and I got a new plot which was on the interval (-2, 1) not (-1, 1). I keep editing the cell and trying to re-evaluate the plot and get just continue to get incorrect domains or unchanged plots.

It seems like something is going on with cached images, or old images being re-displayed.

I finally figured out that I can solve the problem by cutting and pasting the code into a new cell, changing the name of the function to something different like h(x), and evaluating the cell.

Any thoughts on why this is happening or how I can prevent it from happening in the middle of class? Do I need to completely log out / log in to the server every time my IP address changes? Or maybe this problem is completely unrelated to the network change.