Can Excel Create Plots Using Equations?

[Benny]

Hi I'm currently working on an assignment and one of the questions requires me make a plot of the following. I am told that Excel can produce the plot but I don't know how to enter the equation.

$$x_{n + 1} = \frac{{11.5x_n }}{{1 + x_n ^2 }} - \lambda ,x_0 > 0$$

A few values of lambda are specified. If there is a way to plot this on Excel? Any help would be great thanks.

Note: I hope this isn't the wrong forum for this question.

 

[hotvette]

I use Excel for plotting all the time, but there is no capability I know of to just give it an equation. What you have to do is calculate the x,y values, highlight them, and click the plot button.

Unless I don't understand correctly, this is just a set of parametric equations in lambda. What I'd do is have several columns, one corresponding to each value of lambda. Each row will be successive calculations of $x_{n+1}$. If you know lambda, all you need is a starting value for $x_n$.

Did I miss something?

 

[Benny]

Yeah I've been given some specific values for lamda lie 0, 3, 6 etc. So if I wanted to plot this would need to calculate each value? As in for example I start with x_0 = 2. Then x_1 = some value. For the next point I would need to calculate x_2 = f(x_1) and so on? I just thought that there was some kind of shortcut to generating the values because I think that we're supposed to generate a whole bunch of values.

 

[faust9]

Do you know how to use the quick fill corner?

 

[hotvette]

Yeah I've been given some specific values for lamda lie 0, 3, 6 etc. So if I wanted to plot this would need to calculate each value? As in for example I start with x_0 = 2. Then x_1 = some value. For the next point I would need to calculate x_2 = f(x_1) and so on? I just thought that there was some kind of shortcut to generating the values because I think that we're supposed to generate a whole bunch of values.

Oh, but it is sooooo easy. Let me give you an example. Let's say x_0 is 2. Put that in cell A1. In cell A2, you want to calculate x_1, but I'll make up the formula just to make it simplier. Let's say x_n+1 = x_n^2 + 3*x^n + 5/3. In cell A2 you type (literally): =A1^2+3*A1 +5/3 and hit enter. Highlight cell A2, click copy, and highlight cells, A3 through A100 and click paste. That's all there is to it!

 

[Benny]

Oh ok, I didn't know that it could be done so easily. I'm pretty clueless when it comes to computers, apart from things related to fps. Thank you very much for your help.

 

[hotvette]

Check out the edit in my previous post. I gave an example of the very thing you are trying to do. Notice the formula has A$1. That means as you paste the formula down, the 1 remains fixed, meaning in this case, it is lambda.

Excel is one of the most amazing applications I have ever seen.

Check this out.

http://www.usd.edu/trio/tut/excel/

 

[Dr Transport]

hotvette,

how'd you get the formulas to show up in your attached picture?

That is something I've been wanting to do at work to help check my analysis...

dt

 

[Andre]

`Toggle formula's or values with <ctrl>+ ` that's the upper left key on my keybord, left of the "1", the graph accent underneath the ~.

 

[Dr Transport]

Cool...Thanks