This is a very hard problem and there will not be a J primitive for it.
A J script would be welcome.
Henry Rich
On 11/4/2020 10:58 PM, Piet de Jong wrote:
I was hoping for more of a “J” type solution.
For example if f(x,y) = (x^2 + log y)^{-1} = c
Then given c and say x, I can solve for y. (ie write J function)
Or given c and y I can solve for x. (ie write a J function)
(I’m assuming domains etc are ok. — this is just an example.)
So instead of following this long process of finding the two functions I was
hoping in J there would be a “clean and tidy” way of doing things.
Probably impossible even for simple functions f.
On 5 Nov 2020, at 2:24 pm, Raul Miller <[email protected]> wrote:
The answer is: sometimes yes, sometimes no.
See https://en.wikipedia.org/wiki/Equation_solving for some of the issues.
If f can be expressed as a polynomial, you might want to consider
using https://www.jsoftware.com/help/dictionary/dpdot.htm
Thanks,
--
Raul
On Wed, Nov 4, 2020 at 7:27 PM Piet de Jong <[email protected]> wrote:
Still trying to learn/improve my J after 25 years.
Here is the issue. I’m probably having a pipe dream.
Suppose you have an implicit function f(x,y)=0 which is relatively “clean” (ie
simple to specify)
Is there a “clean/efficient” way in J to solve for y given x or vice versa.
I know I can write a function g such that g x gives y and g^:_1 y gives x.
But is there a cleaner way? The g and its inverse may be complicated even if
f is relatively simple.
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