Tracing a point on a graph and displaying the y value - Mathematica

[chris_0101]

Hey,

I am using Mathematica 8 and I finally figured out how to drag a point along a graph using a slider bar, which increases or decreases the x value. Now, I am stuck on how to display the y value for the changing x value on the screen.

My code is below:
parabola = Plot[x^2, {x, -4, 4}, Ticks -> False]

Manipulate [Show[parabola, Graphics [{Red, Disk [ {x, x^2}, 0.05]}],
PlotRange -> {{-4, 4}, {-4, 4}},
AspectRatio -> Automatic], {x, -4, 4}]

An image of my code

Any help is appreciated,

Thanks

 

[mmwave]

!



It looks like you are on the right track with your code. In order to display the changing y value on the screen, you can use the Epilog option in your Manipulate function. This allows you to add additional graphics or text to your plot. In your case, you can add a Text object that displays the y value for the current x value being shown by the slider bar. Here is an example of how you can modify your code to achieve this:

parabola = Plot[x^2, {x, -4, 4}, Ticks -> False]

Manipulate[
Show[parabola, Graphics[{Red, Disk[{x, x^2}, 0.05]}],
PlotRange -> {{-4, 4}, {-4, 4}}, AspectRatio -> Automatic,
Epilog -> {Text["y = " <> ToString[x^2], {3, 3}]}],
{x, -4, 4}]

This will display the y value for the current x value at the coordinates (3,3) on the plot. You can adjust the position and formatting of the Text object as needed. I hope this helps. Keep exploring and experimenting with Mathematica, it is a powerful tool for scientific computing.