On Sun, Apr 03, 2011 at 07:02:36PM +0100, Leo Butler wrote:
> < Daniel> 1) Is it possible with maxima to find the local minimums/maximums of a
> < Daniel> graph, along with the absolute/global minimum and maximum? I'm using the
> < Daniel> command line interface...
> <
> < If you have a symbolic expression, can't you compute the derivative
> < and use a numerical method to find the zeroes? You can try solve or
> < mnewton or minpack_solve to find the zeroes.
We haven't covered this in our course yet. I was hoping their was a
function available like to the other students just to return the
points... I'll run this by my teacher anyway.
> < Daniel> 2) When graphing with maxima, what is the best way to choose a suitable
> < Daniel> x range for the plot2d argument? Is it possible to mark the major points
> < Daniel> of my graphs (tp, min/max, end points, intercepts intersections etc.?)
> < Daniel> Is there anyway to permanently set some variables like gnuplot_term so I
> < Daniel> don't have to type so many arguments for the plot2d command?
> <
> < Look at set_plot_option. You can set things like gnuplot_term there.
That sounds like what I was looking for, thanks.
> < Daniel> 3) Suppose I have 5 (x,y) coordinates. On the standard casio devices at
> < Daniel> school these points can be punched in and the user may trial a linear,
> < Daniel> quadratic or cubic equation to see which is the best fit for the
> < Daniel> points. The calculator provides a number of how successful the equation
>
> Btw, a cubic always fits at least as good as a quadratic which fits in
> turn at least as good as a linear model. If your calculator tells you a
> linear model fits better than a cubic one, this is because it is using
> some measuring stick other than goodness-of-fit.
So for examination purposes there is no point trying any other fit than
a cubic?
> < Daniel> was eg. linear, quadratic or cubic. Is it possible to find the equation
> < Daniel> for a set of points with maxima?
> <
> < Sure, but it looks like there's nothing completely builtin. You can
> < do a least-squares fit using lbfgs or minpack_lsquares to produce the
> < equation. But you'll have to set up the equations appropriately
> < before calling these routines.
>
> Here is a function that does the job, using the lsquares package.
>
> (%i2) load(lsquares);
>
> (%o2)
> "/home/work/maxima/sandbox/git/maxima-git/share/contrib/lsquares.mac"
>
<snip>
Thanks very much, when I get home I'll play with this...:)
I suppose your defining the function here? Is there any way to put this
into a file or something so it doesn't need to be done each time?
Anyway, I'll have a go at it when I get home this afternoon.
Thanks very much for your help,
Dan