Show you can save and execute a file. Due before Tuesday's class (9/14)
Get a floppy disk and put "Math 320" and your name on it. This disk
will hold your work for the entire semester.
First save the two files junk.m and counter.m on your floppy
The file "junk.m" is a script file that solves a linear algebra
problem, Ax=b. Open matlab and execute this file by typing "junk" at
the matlab prompt.
When you start matlab, it will be in the wrong directory for your
purposes. You saw the error message
"Undefined variable or function `junk'." when you typed "junk". If
this happens, type "pwd". This will show you what directory you're
presently in. Move to the correct directory with the command "cd d:"
(to get to the d drive, if that's the name of the floppy disk drive.)
In general, "cd .." will move up one level. "cd Math320" will move
into the directory Math320 if it's there. To see what's around, type
"ls". If you see junk.m and counter.m, then you've arrived.
The file "counter.m" is a file that creates a vector x, which is those
integers from a to b. Open matlab and execute this file by typing
"[x] = counter(3,50)" at the matlab prompt. (Or whatever numbers you
Once you have succeeded in doing this, come find me. We will go to
the computer room and you will demonstrate the above to me.
Matlab looks for files that end in "*.m". When you create a file for
matlab, it must end with .m To execute the file, you type the part of
the file name that comes before the .m Your file names can have pretty
much anything in them, but only one period. (You can't have a
file called "test.this.m".)
You have to be careful in the naming of .m files since there are some
names already used by matlab. For example, "rand.m" is a built-in
file that creates matrices with random entries. If you create your
own file called rand.m then you will never be
able to execute it. Whenever you type "rand", you'll get matlab's
rand.m To test if your filename is a good one, say "my_dog_fluffy.m",
type "help my_dog_fluffy" at the matlab prompt. If matlab has such a
file built it, it will tell you about it. (If you type "help rand" it
would tell you all about rand and how to use it. It will give you the
names of other commands you might be interested in.)
The two files "junk.m" and "counter.m" are
of different types:
junk.m is a script file, which is a file that contains a
sequence of matlab commands. If you're going to have to type the same
10 commands in a row, but with minor modifications each time, then
it's fastest to write a script file, like junk.m, and then use an
editor to type those minor modifications in and then rerun junk.m,
rather than typing the 10 commands over and over again.
counter.m is a function file. It takes two inputs,
the integers a and b, and gives you back a vector, x. Now that
you have x, you can do all sorts of things with it.