Need help with RPL Listing for "SOLVER FOR ANY VARIABLE"

[Claudio L.]

(07-07-2019 08:45 PM)Namir Wrote:  Hi All,

I have a presentation for HHC2019 that Richard Nelson asked me to do. It is a multi-variable solver. Meaning that given an equation with N variables, you can solve for any variable given fixed values for the remaining N-1 variables.

I would like an RPL version (see teh HP-71B and HP-4C versions that solve for any variable in simple financial equation FV=PV*(1+i)^n).

I will give credit to the author of the author of the version I will use in my presentation. I will also mention that author in my presentation that will appear on YouTube.

The "white menu" solver in the 48/50 series does exactly what you are looking for, and with the best (in my opinion) open UI you can get for a solver: just assign values to some variables and solve for others, clean and simple, and no RPL code needed.
The other numerical solver in the 50g can also do that with a different UI (more visual, in my opinion less practical to assign values to variables quickly), also no RPL code needed at all. There are some programmatic ways of using the same built-in solvers, but honestly with two different user interfaces, it's hard to justify writing a program to do it.
You also have available the multiple equation solver, for multiple variables in multiple equations so there's even less need for RPL code. If you still want RPL code, it only needs to store the equation and call the proper menu number to activate the "white menu" solver:

Code:


<< 'FV=PV*(1+i)^n' 'EQ' STO 30 MENU >>

By the way, if it's only the financial equation you are interested in solving, the 50g has the full TVM solver, just setting the payment amounts to 0 you end up with the equation above. That also has a nice UI built-in.