Mathematics tools

Hi Ben!

Very nice that you're interested in STACK! To try to answer a few of your questions:

1. Deployment is connected to randomized questions. If you author a question with random parameters, then the solution of the problem might depend on the values of the parameters in an undesired way. The students get randomly chosen instances among those that you have deployed. Questions not using randomization don't need to be deployed.

2. The question note is also used with random questions. STACK uses the question note to distinguish between two random instances of the same question, e.g. when deploying. And this is also useful for reviewing after your course is done. The question note should include all random variables. Personally, I would write something like "Derivative of @expression@ is @diff(expression,x)@", if expression is a random function of x that should be differentiated. I don't know if that is good or bad, but that's how I started doing it. I'm not sure it's a good idea to make entering the question note automatically, since it might not be easy to read later, when you review.

3. You can already now plot things, with or without randomization, using the plot command.

4. The point of the automated question tests is to automatically test the functionality of your question, and try to make sure that you don't accidentally break something by editing your question. Therefore you should add at least one test case for every possible way of traversing the potential response trees (PRTs), in order to make sure that the outcome is the correct one for a given input. I don't see how you can replace this by adding cases to the PRTs, because the question tests are precisely supposed to verify that these PRT cases work properly. Indeed, you should try to predict what mistakes a student could make and add tests that capture these in the PRTs. Here the answer note is again useful for reviewing.

5. A screen cast would be very good! Please post the link if you create something! These Authoring quick start questions should get you up and running very quickly.

6. I didn't understand your comments on CAS text. If I'm not mistaken, then the CAS text is precisely what goes between the @ signs. See here. In the CAS Chat, you need to enclose whatever you want Maxima to evaluate between @ signs, IIRC. In your case, type in @3-1;@ and see what happens.

7. About the input and answer tests I don't know, that's a question for Chris and Tim, I guess.

Hope this can be of some help,

Mikael

Mikael, Thanks for your reply. 

Ben, the 'test suite for validation of student's input' is as much to inform teachers what STACK considers valid!  Yes, I used as many examples as we could think of, including a whole suite used by the NUMBAS project.  Some of the "fails" are conventions.  For example, "sqr(x)" isn't recognized, but might be meaningful to some people.  Similarly, "sgn", "gcf" are not STACK functions.  It will be impossible to please everyone because there are conflicting conventions.  We will try to provide options where these can be solved. The OU have a separate input pannel project which we will hook STACK to in the future.  This is an important issue. Please send me your examples of syntax issues, and requests for changes. 

In practice, our planned reporting mechanism will generate a report of all "invalid" expressions, so we can work from cases which arise in use.

There are "failures" on 'the suite for STACK Answer test'.  I get two fails where the sqrt function interacts with complex numbers %i, which are in the AlgEquiv test and are flagged as "these test currently fail".  There are some very interesting branch cut issues here!  These are probably not going to arise in practice, but might so I've been honest.  Again, I hope these lists indcate how STACK behaves. 

What is your third failure?

Chris

Thank you very much.  An updated Japanese translaton would be very welcome.

Chris

Solved! It was a permissions issue in Maxima's directory (/usr/lib/maxima/).

This surprises me. it gives me an error in red each time I forgot to do it. Maybe I was on another browser. However I had to scroll to the field where the error was to actually see that there was an error. 

Steve,

I'm sorry you ran into this problem.  We certainly tried to put plenty of checks to help teachers write questions and if the question variables contain "rand" then the answer note must be non-empty.

I wonder if this problem is the CSS and browser, rather than STACK.

Chris

I'm not sure why I am seeing this issue and others apparently aren't.  To help you run it down, here is what my system looks like:

STACK version: 2012070300

Moodle version: 2012062501; Release 2.3.1 (Build: 20120706)

I have a pretty vanilla system in terms of appearance and CSS.  I have been testing this using the standard theme with no extra CSS added.  I set up the quiz with 2 attempts allowed, Grading Method: highest grade, all questions on one page, and adaptive mode for feedback.

The feedback options were as follows:

For me text question, I set the question variables as follows:

b:rand(5)+1; 

The question was written as:

What is @b@+1?

[[input:ans1]]

If I don't misremember, variables can be one letter only in Stack. Things with multiple letters are interpreted as functions. To type a psi, I would use latex: $\psi$, does that not work for you?

I don't really understand this bit of the system, we will need to wait for enlightenment from Chris, but 'PSI' is listed in the $teachernotallow array in stack_cas_casstring, and it is a Maxima function/operator/reserved word or something.

So, bascially, you cannot use it.

Steve,

Yes, "psi" isn't available as a variable name because it has already been defined as 

"The derivative of log (gamma (x)) of order n+1. Thus, psi[0](x) is the first derivative, psi[1](x) is the second derivative, etc." 

If something like this doen't work, then check in Maxima if it is already defined.  

It does appear possible to re-define functions etc, but since this will have all sorts of unexpected side effects I decided it would be better not to allow question authors to do this. I appreciate in this case you need to use the letter as a variable as you might "x" etc.  I'm not sure what to do here, but I'll give it some thought as this is a perfectly sensible request. 

Chris

Bulk deploy is already on the todo list. (https://github.com/maths/moodle-qtype_stack/blob/master/doc/en/Developer/Future_plans.md)

Can you:

1. Export the question as Moodle XML format, and

2. Tell us an exact sequence of actions to perform on the question in the preview window, to make the problem happen.

It is fine to report bugs here. You can also use https://github.com/maths/moodle-qtype_stack/issues if you prefer.

Are you using the same version of Maxima on both servers? I noticed that (at least some of) the newer versions of Maxima start up very slowly. At this time I think STACK starts a new instance of Maxima quite often and this could perhaps explain your problems.

Better ways of connecting to Maxima are being investigated. In the meantime, I solved the problem by installing an older version 5.23.2 of Maxima and optimised it as described here. See in particular the bottom of that page; if I was to set up my server today then I would certainly look into the maxima pool servlet.

Does this help at all?