# Python How to make an animation in SymPy using Python

#### JD_PM

I want to make an animation where a (red) ball departs from (0,0) and draws the function $f(x) = sin x$

This is what I know:

How to plot $f(x) = sin x$

To do so I followed instructions from the worksheet. Actually I'd have done:

But I guess they want to me to it in that way because I have to do less work while coding for the red dot to draw the entire sine curve.

Now to plot just a piece of the function:

If we set i=50 and x runs from 0 to 200, we are aiming at plotting just 1/4 of $f(x) = sin x$ .

The line ax.plot(X, Y, 'o', color='red') locates the point at i=50 (I guess 'o' is just the command for the point).

But now, how can I code such an animation of $f(x) = sin x$ from (0,0)? I have read I should import:

import matplotlib.animation as animation

I've been looking for exercises on animations in SymPy in Python but found nothing.

Any help is appreciated.

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#### lomidrevo

I think that SymPy has nothing to do with animations. It is a functionality of matplotlib. You may want to check this link describing it. You can find there several examples, providing full code. It should be easy to pick one and rewrite it for your needs.

#### JD_PM

I think that SymPy has nothing to do with animations. It is a functionality of matplotlib. You may want to check this link describing it. You can find there several examples, providing full code. It should be easy to pick one and rewrite it for your needs.
Thanks, in that link I found what I was looking for. There's a final issue now.

How can I make the leading point red?

#### lomidrevo

You should have second line element (matplotlib.lines.Line2D) for the red dot to be updated in your "update" function. In the third line of the code from your screenshot, you get only one line element, that is your blue line. So you should create an empty list of the line elements and using the "append()" method to add new line elements as many as you may need them to update.

Here is an example (including also a text field updated in the graph):

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