Here is the question im having problems with, i dont know even where to start. All the examples dont use real numbers.
"A data sequence {0.47, 2.61, 1.63, -0.98, 0.23, 1.12} is first quantized by a scalar quantizer shown below, and then coded by the arithmetic coding. Assume the probabilities for the outputs of the quantizer are P(-1.5)=0.2, P(-0.5)=0.3, P(0.5)=0.4, P(1.5)=0.1, calculate the tag value to represent this data sequence."
example-5.png
input = {0.47, 2.61, 1.63, -0.98, 0.23, 1.12}
output = {0.5, 1.5, 1.5, .......}
All I did there was to look on the graph for the input data (eg, the first in the sequence is 0.47), then go directly up from the input axis at that point to where you meet the line representing the quantizer function, and look across to see that at that input value, you get an output of 0.5. Repeat for the other items in the input sequence.
Now, that output sequence contains the "symbols" that you will encode, and the probabilities of getting each "symbol" is what was given to you, eg.
P(-1.5)=0.2, P(-0.5)=0.3, P(0.5)=0.4, P(1.5)=0.1
Check out this link, http://en.wikipedia.org/wiki/Arithmetic_coding in particular the section directly under the heading "Defining a model". This describes what to do with those probabilities and the sequence of symbols that I started working out above. Note: just because the wiki pages uses words for the symbols (such as NEUTRAL, NEGATIVE, etc) makes no difference to your situation, it is just that you have numbers to describe the symbols (such as -1.5, 0.5, etc)
If you still have questions about either of these steps, come back and let us know.