I have some questions about linear

algebra problems, particularly in

connection with matrices.

I've written some problems that ask for

matrices, or bases for certain linear

spaces of matrices, hoping to not give

away the number and shape of the

matrices required.

The Matrix type (Value::Matrix, I think)

works for not giving away the shape.

However, if a student is completely lost

and enters, e.g., (1, 2, 3) where a matrix

should go, the problem throws a mean

error. (It seems that cmp tries to apply

"$student->dimensions" before checking

that the student's answer is a matrix,

and chokes on the point.)

As well, I was unable after a few minutes

to compare a student's answer to a List

of matrices (not giving away the number

of matrices in a basis). I could manage

using a MultiAnswer, but of course that

gives away the (maximum, at least)

number of matrices in the list.

Finally, I was unable after a few minutes

to apply basis_cmp to a single answer blank

(into which would go a list of matrices)

or a MultiAnswer, so I resorted to ad hoc

checks.

These issues might be easy to resolve

in ways that I couldn't see quickly. I

am writing these problems on the run

and so I tend to give up quickly and go

to something that is close to what I

want and works. (I can warn my

students that a problem will get

embarrassed and "blush" if they

enter a point where they should

enter a matrix, for example).

Does anyone know of simple and fairly

general ways around such issues? Is

anyone working on these kinds of things

right now? If so, I'd be happy to pitch

in when I get up to speed on how the

current stuff works. (It would be nice,

e.g., to be able to enter and parse

matrices column-by-column, to support

parameters in matrices/polynomials,

to have a matrix-matrix product a la

Artin, where the left factor is a list of

abstract vectors, etc. etc.)

Thanks for any information/comments.

William Boshuck

## WeBWorK Main Forum

### Linear Algebra (Matrix)

This forum has a limit to the number of forum postings you can make in a given time period - this is currently set at 10 posting(s) in 1 day