The following function 

$$f(x)=-2 \cos \left(\sqrt{2} \arccos \left(\frac{x-1}{2}\right)\right)+1$$

has interesting property to form a continuous curve with its own integer iterations. The following image illustrates this property:

![alt text][1]

Here blue is f(x), red is f(f(x)), yellow is f(f(f(x))) and green is f(f(f(f(x)))). It seems that all these functions form a continuous, and, probably, smooth curve.

The question is what is the general criterion for a function to have such property. Can you point some more examples of functions with such property?

P.S. If to use the folowing function 
$$f(x)=-2 \cos \left(\sqrt{2} \arccos \left(\frac{x-1}{2}\right)\right)+1.1$$
the curve becomes as below with one continuous branch and numerous closed circular branches.

![alt text][2]

For function
$$f(x)=-2 \cos \left(\sqrt{2} \arccos \left(\frac{x-1}{2}\right)\right)+0.9$$
the curve is completely continuous and seems to be smooth.

![alt text][3]


  [1]: http://static.itmages.ru/i/10/1201/h_1291177404_9062e5977d.png
  [2]: http://static.itmages.ru/i/10/1201/h_1291214023_dcadf36911.png
  [3]: http://static.itmages.ru/i/10/1201/h_1291213783_96931fa742.png