Matlab -- Venting, Plus Miscellaneous Questions

I have just started using Matlab the past two weeks for a class. You
know, sometimes you get a new package of software, and start using it,
and right off the bat it seems pretty intuitive. That doesn't mean
you never have to look in the manual, or check the Help, but most
things that you seem to need appear right at hand on the menus, or on
context-sensitive pop-up menus, etc.

Matlab is not one of those programs. So far, as far as I'm concerned,
it's a total piece of ***, at least in the user-friendliness
category. It may very well be able to do extraordinary math things,
once you know the program well enough. But nothing that I need to do
is readily apparent, and hunt as I might, I can't seem to find the
answers to many (most?) of the questions that I have in either the
print or online documentation. Damn, I hate programs like this, you
waste more energy trying to figure them out than you put into actually
using the piece of crap.

Okay, I've vented -- and other buyers, beware -- and now maybe some
users will be good enough to help me with some questions.

1. I want to reduce the number of decimal characters the program
shows. I found how you could do that under Preferences for numeric
calculations, but symbolic calculations keep showing some ridiculous
number of decimal places, I haven't even counted. Is there a way to
fix that? Here's some of what I mean:

EDU>> 2/3
ans =
0.66667 %This is okay.
EDU>> eqn = '4/s = (3000 + .033*s + (10^9)/s) * I';
EDU>> Ifr = solve(eqn,'I')
Ifr = 4000./(3000000.*s+33.*s^2+1000000000000.)
EDU>> Itd = ilaplace(Ifr)
Itd =
..72133570773394583167815285220228e-3*exp(-45454.545454545454545454545454545*t)*sin(168038.43191529419942502424397894*t)
% This is NOT okay!!!!

2. Matlab does not seem willing to plot symbolic expressions, or to
convert symbolic expressions to regular numeric expressions. Using
the example just above, can anyone tell me how to get the program to
plot "ltd" as a function of time? (FYI, the calculations come up in
the process of finding the time behavior of a simple RLC circuit.)

3. If you have a symbolic expression like '4/5*exp(-t)*sinh(t)', how
do you tell Matlab to convert the 'sinh(t)' to it's exponential parts,
and then carry through the multiplication with the 'exp(-t)' term?

4. Let's say I do the following:

EDU>> eqn2 = 'x = y + 3'
eqn2 = x = y + 3
EDU>> y=1:2:10;
EDU>> eqn2
eqn2 =
x = y + 3

But wait, that's not what I want! I want a list: 4 6 8, etc. How
do I make that happen? And then on the other hand...

5. Suppose I now enter:

EDU>> z = y+3
z =
4 6 8 10 12

Okay, that's good... but suppose I want to be reminded of my
definition of z? How do I get that back again, without have to scroll
through the command history?

6. Is there any way to tell the command history to stay at the
currently highlighted command, rather than autoscrolling to the bottom
each time I enter a new command?

7. Is there a way to save and restore, not the data, but the
sequence of commands and responses in the command window? So that I
can open the command windows, and fully restore all those commands?

That's all for now. (I'll spare you my plotting problems, at least
for now.) I'm sure there will be more to follow. I'm looking forward
to hating this program even more as time goes by.

Thanks in advance for all replies.

Steve O.


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