Re: Evaluating quadratic functions

[Paul Laub]

Tom,

Try replacing the exponentiation operator  ^  with the element by
element exponentiation operator  .^  (dot caret).  Using ^ alone
computes a matrix power. For that a square matrix is needed. Note that
for a = [1 2; 3 4] ,  a ^ 2  and a * a give one and the same answer,
while a .^ 2 and a .* a give one and the same different answer. a must
be square for the former but not necessarily for the later.  All are
correct. Which is appropriate, though, depends on your purpose.

Paul Laub 


On Mon, 24 Jan 2005 01:50:38 +0000, address@hidden
<address@hidden> wrote:
> I'm having trouble understanding how to evaluate and plot quadratic functions.
> Here's a sequence that explains what I'm trying to accomplish.  In particular,
> I don't understand the error message "error: for A^b, A must be square" It 
> doesn't
> seem that A being square has anything to do with the function.
> 
> Can anyone help me understand how to do this?
> 
> Thanks,
> 
> -- Tom
> 
> GNU Octave, version 2.1.50 (i686-pc-linux-gnu).
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> Report bugs to <address@hidden>.
> 
> octave:1> x = 1:1:2;
> octave:2> sqrt(x)
> ans =
> 
>   1.0000  1.4142
> 
> octave:3> exp(x)
> ans =
> 
>   2.7183  7.3891
> 
> octave:4> function retval = linear(x)
> > retval = x + 1;
> > endfunction
> octave:5> linear(x)
> ans =
> 
>   2  3
> 
> octave:6> function retval = quad(x)
> > retval = x^2;
> > endfunction
> octave:7> quad(x)
> error: for A^b, A must be square
> error: evaluating binary operator `^' near line 2, column 11
> error: evaluating assignment expression near line 2, column 8
> error: called from `quad'
> octave:7>
> 
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