rowops.py

rowops.py is a keyboard-driven interface for manipulating a matrix with the three elementary row operations.

This tool was created for students in a linear algebra course who are doing things like practicing the reduction of a matrix into reduced row echelon form. Using rowops.py is way faster than practicing by hand or with a calculator.

What are some cool features?

• undo! If you manipulate by mistake, use u to undo.
• a manipulation log. If you worked on a long problem, use l to print out all the steps you took to get there.
• fractions. No ugly decimals. You can use fractions for input too.

How do I use it?

Run rowops.py by entering python rowops.py on your command line. You'll get a console that looks like:

Use the '?' command for help.
> 

The > symbol means the program is ready for you to start a new command. You can type ? and hit enter to list all of the available commands.

> ?
  n - create a new matrix
  s - swap one row for another
  m - multiply a row by some value
  a - add a multiple of one row to another row
  u - undo the latest change to the matrix
  r - revert the matrix to its original state
  p - show the current matrix
  l - show a log of your changes to the current matrix
  ? - show this list of commands and their descriptions
  q - quit the program

Give me a walkthrough, please.

For practice, you can try creating a new matrix by using the n (for new) command. In our example, we create a 3x2 matrix. The process looks like this:

> n
Create a matrix with n rows and k columns.
How many rows? 2
How many columns? 3
Enter your data one row at a time, separating the numbers with spaces.
R1: 1 2 3
R2: 4 5 6

Result:
R1  1 2 3
R2  4 5 6

Any command that creates or changes a matrix will print out the result. Let's halve the second row with the m command. Notice that rowops.py supports fractions!

> m
Multiply a row.
Row: 2
Multiplier: 1/2

Result:
R1    1   2   3
R2    2 5/2   3

We add -1 times row one to row two...

> a
Add n times row A to row B.
Multiplier: -1
Row A: 1
Row B: 2

Result:
R1    1   2   3
R2    1 1/2   0

The last elementary row operation is swapping rows. That's easy:

> s
Swap two rows.
Row A: 1
Row B: 2

Result:
R1    1 1/2   0
R2    1   2   3

Let's print a log to see all of our great work in one place!

> l
Create a new 2 by 3 matrix.
R1  1 2 3
R2  4 5 6

Multiply R2 by 1/2
R1    1   2   3
R2    2 5/2   3

Add -1 times R1 to R2
R1    1   2   3
R2    1 1/2   0

Swap R1 with R2
R1    1 1/2   0
R2    1   2   3