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[✓] Plot and print out values of a function in NestList?

Posted 1 year ago
6 Replies
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Hi, I'm new to Mathematica and I'm having troubles in understanding how to evaluate a custom function that I applied NestList to. Here's my function:

f[x_, m_] := m*x /; 0 <= x < 1/2
f[x_, m_] := m*(1 - x) /; 1/2 <= x <= 1
x = 0.2
m = 2

Next I got NestList like this:

NestList[f, {0.2, 2}, 4]

which have given me following output:

{{0.2, 2}, f[{0.2, 2}], f[f[{0.2, 2}]], f[f[f[{0.2, 2}]]], 
 f[f[f[f[{0.2, 2}]]]]}

Now instead of printing f f f .... f f I'd like to see actual values of the function f after evaluation such as {value 1, value 2, value 3, ..., value n}. Moreover I'd like to plot such a NestList where values in NestList would be coordinates of n points on axis.

Any help, advice or example would be greatly appreciated.

EDIT: I'm studying Dynamic systems and trying to compute and plot so called "tent map"

6 Replies


You defined the function f incorrectly. If you want to pass it a list of two arguments your pattern must be a list. Also, all patterns for named variables must have underscores after them:

f[{x_,m_}] :=



![][1] I don't know what i did wrong but still i have the same problem. Do you know where could be a problem?


f operates on a list the first time, it returns a single number, then you send that number to f again. The function f does not know what to do with a single number unless you define another function of f that takes one number. You can see this in your output because you have f[.4] for example.

I am not really sure what you are trying to do.

One simple fix is to have f return a list with your value from above followed by m. Now the Nest will work.

f[{x_,m_}] := {m*x /; 0 <= x < 1/2, m}

(Same for other function)

Now the Nest will work.


Posted 11 months ago

Thank you for your help.

Finally was enough to use just this as you can see on the picture.

enter image description here

@Nikol Skorupova, please do not post code as images. This clearly explained in the forum rules:

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