1:
2: For LON-CAPA, one of the most important functions is the \texttt{random}
3: function. Random takes three parameters: a \emph{lower limit}, an \emph{upper
4: limit}, and an \emph{interval}. The \texttt{\&random} function returns a
5: random value between the upper and lower limit, some integer number of \emph{interval}'s
6: away from the lower limit. Thus, for example, \texttt{\&random(1,2,.2)} might
7: return 1, 1.2, 1.4, 1.6, 1.8, or 2. \texttt{\&random} uses a uniform distribution.
8: Other distributions are available in LON-CAPA, and can be found by consulting
9: the function list.
10:
11: %
12: \begin{figure}
13: \begin{lyxcode}
14: \$a~=~\&random(1.0,10.0,1.0);
15:
16: \$b~=~\&random(-10.0,~-3.0,~1.0);
17:
18: \$answer~=~\$a+\$b;
19: \end{lyxcode}
20:
21: \caption{Sample \texttt{random} Calls \label{Sample Random Calls figure}}
22: \end{figure}
23: If you put the script in ``Sample Random Calls'' into the
24: \textbf{Script} block (replacing whatever contents might be in the block
25: already), you'll get two random variables \$a and \$b. Now, in the \textbf{Text
26: Block}, put {}``What is \$a plus \$b?'', and in the \textbf{Answer} put
27: {}``\$answer'', without the quotes for either of them. (It is a good idea
28: to create a variable to hold the answer and call it \$answer, or some other
29: reasonably standard name. Do not try to compute the answer in the \textbf{Answer}
30: field itself; it will not work as you expect.) Now save the problem and \textbf{View}
31: it. You'll see a randomized problem.
32:
33: For each student, the same random number will be used each time they visit
34: the problem, but each student will get different random numbers. For any
35: but the simplest random problems, you'll want to see several random problems
36: to make sure everything is working out correctly. This is what the \textbf{Random
37: Seed\index{Random Seed}} field is for. To see another randomized version
38: of the problem you've just created, put another number into the \textbf{Random
39: Seed} field and hit \textbf{Change}. It doesn't really matter what number
40: you put into the field. But for any given \textbf{Random Seed} with the same
41: problem, you'll see the same randomized problem generated for you. (If you
42: change the \textbf{Script}, you are no longer guaranteed to get the same
43: problem.)
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