Is 3D graphing still on HP's Prime to-do list?

[Joe Horn]

(09-12-2015 05:59 PM)Parmenedes Wrote:  So why would the CAS use lowercase variables at all?

Good news and bad news.

The Good News: There is a good reason, actually. CAS is able to perform symbolic math, to answer questions like "What are the binomial factors of 15x^2-2x-24?" This obviously requires the use of undefined variables, that is, variables to which no value has been assigned. The Advanced Graphing app, however, is not intended for symbolic math at all, but rather for creating a visual approximation of real-number approximations. This obviously requires the assigning of real values to real variables.

So CAS has to use undefined variables to perform symbolic math, and graphing has to use real variables with real values in them.

It was decided by the Prime design team to address this dichotomy by building in 27 permanently defined real variables (A-Z and θ) and using them for graphing, and then letting CAS use anything undefined (including lowercase letters, but not limited to that) when undefined variables are needed.

The Bad News: This results in the experience you described (we've all experienced it), namely, we use CAS to perform some nifty symbolic math (using undefined lowercase variables of course, because the uppercase variables always have values in them so they can't be used for symbolic math), then tried to graph the result... only to get an error because the grapher wants real variables (because it has to store reals in them).

It's annoying. Having an understandable reason only makes it slightly less annoying.

(09-12-2015 05:59 PM)Parmenedes Wrote:  It seems like it would be better to have the Prime be consistent across the whole system.

It can't be consistent, for the reason explained above. However, IMHO the unfortunate result of this dichotomy (that CAS results can't be directly graphed without manually editing the variables) should be addressed by the design team.

Brainstorm from Captain Obvious: Wouldn't it be cool if the graphing apps automatically converted all lowercase x's and y's to uppercase X's and Y's? Can anybody foresee any problems that such automatic conversion might cause? It would solve this problem of using CAS results in the graphing apps.