> No, %o4 is a symbolic expression with a "free variable" x in it.
>
> What you define in %i2 is a function f, which when called, computes afresh,
> an interpolating function to go through three points. So, even though the
> points don't change, the computation is done again, and a new symbolic
> expression is returned, always equal to the previous one. That is why %o3
> and %o4 are the same.
So, it seems silly to define
f(x):= linearinterpol([[2,1],[3,2],[4,1]])
Rather, it seems more appropriate to use
expr_1: linearinterpol([[2,1],[3,2],[4,1]])
Since I am generally interested in using the actual interpolating
function, what is the best way to define it?
Also, what exactly is a 'symbolic expression with a free variable' ?
How does it differ from the rhs of
f(x):= x^2 + 2*x;
Apparently, maxima treats them differently.
TIA,
-sen
>
> RJf
>
>> Otherwise, how does one multiply by the real numbers in the
>> expressions?
>>
>> So, it seems that the natural thing is that after entering the (%i4)
>> operation, one should be able to do f(2), f(%pi), etc.
>>
>> But, here is what happens.
>>
>> (%i1) load(interpol);
>> (%o1) /usr/local/share/maxima/5.12.0/share/numeric/interpol.mac
>> (%i2) f(x):= linearinterpol([[2,1], [3,2], [4,3]]);
>> (%o2) f(x) := linearinterpol([[2, 1], [3, 2], [4, 3]])
>> (%i3) f(2);
>> (%o3) (x - 1) charfun2(x, minf, 3) + (x - 1) charfun2(x, 3, inf)
>> (%i4) f(4);
>> (%o4) (x - 1) charfun2(x, minf, 3) + (x - 1) charfun2(x, 3, inf)
>>
>>
>> So, one has to do an extra evaluation like
>>
>> %i5) linearinterpol([[2,1], [3,2], [4,3]]);
>> (%o5) (x - 1) charfun2(x, minf, 3) + (x - 1) charfun2(x, 3, inf)
>> (%i6) f(x):= ''%;
>> (%o6) f(x) := (x - 1) charfun2(x, minf, 3) + (x - 1) charfun2(x, 3,
>> inf)
>> (%i7) f(2);
>> (%o7) 1
>> (%i8) f(3)
>> ;
>> (%o8) 2
>> (%i9) f(2.4);
>> (%o9) 1.4
>>
>> Why is this necessary?
>>
>> TIA,
>> -sen
>>
>> On Tue, 12 Jun 2007, Robert Dodier wrote:
>>
>>> On 6/11/07, sen1 at math.msu.edu <sen1 at math.msu.edu> wrote:
>>>
>>>> (%o4) f(x) := (0.3 x - 0.02) charfun2(x, minf, 0.2)
>>>> + (1.9 x - .8999999999999999) charfun2(x, 0.9, inf)
>>>> + (1.7 x - .7199999999999995) charfun2(x, 0.8, 0.9)
>>>> + (1.5 x - .5600000000000003) charfun2(x, .7000000000000001, 0.8)
>>>> + (1.3 x - .4200000000000002) charfun2(x, .6000000000000001,
>>>> .7000000000000001) + (1.1 x - 0.3) charfun2(x, 0.5,
>> .6000000000000001)
>>>> + (.8999999999999998 x - .1999999999999999) charfun2(x, 0.4, 0.5)
>>>> + (.7000000000000002 x - .1200000000000001) charfun2(x, 0.3, 0.4)
>>>> + (0.5 x - 0.06) charfun2(x, 0.2, 0.3)
>>>> (%i5) f(2);
>>>> (%o5) 2.9
>>>> (%i6) plot2d('(f(x)),[x,0,1]);
>>>>
>>>> Why does one need the apostrophe and the parentheses in
>> the expression
>>>> in (%i6), and what does it mean?
>>>
>>> In Maxima 5.11 and earlier, a Boolean expression could only
>>> evaluate to true or false, otherwise it would trigger an error.
>>> e.g. when x is not yet assigned a value, if x > 0 then foo else bar
>>> triggered an error.
>>>
>>> The quote mark around f(x) is probably intended to prevent
>> that error.
>>> It doesn't appear to be needed in Maxima 5.12.0.
>>>> From what I can tell, plot2d(f(x), ...) works OK.
>>> (So does plot2d(f, ...), which also works in some, maybe all,
>>> pre-5.12 versions.)
>>>
>>> I guess the documentation can be updated to cut out the quote mark.
>>>
>>> HTH
>>> Robert
>>>
>>
>> --
>>
>> --------------------------------------------------------------
>> -------------
>> | Sheldon E. Newhouse | e-mail:
>> sen1 at math.msu.edu |
>> | Mathematics Department |
>> |
>> | Michigan State University | telephone: 517-355-9684
>> |
>> | E. Lansing, MI 48824-1027 USA | FAX: 517-432-1562
>> |
>>
>> --------------------------------------------------------------
>> -------------
>> _______________________________________________
>> Maxima mailing list
>> Maxima at math.utexas.edu
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>>
>
--
---------------------------------------------------------------------------
| Sheldon E. Newhouse | e-mail: sen1 at math.msu.edu |
| Mathematics Department | |
| Michigan State University | telephone: 517-355-9684 |
| E. Lansing, MI 48824-1027 USA | FAX: 517-432-1562 |
---------------------------------------------------------------------------