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Jazzvocation
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User Variables in Solve App

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I'm having difficulties using the Solve App with user variables that I defined. The Solve App doesn't want to solve for any of my user variables. Although it does work fine with the home variables, I would like to be able to use multi-letter/number variables that I define. 

I realized that using the solve() command in CAS seemed to solve the system. But I noticed that sometimes, having a value already stored in one of my user variables and then solving, the calculator would add or subtract the stored value into the solution value for that variable. In other words, only zero could be stored in the user variable to get the right answer.System of EquationsSystem of EquationsWill not solve for AB and ACWill not solve for AB and ACCorrect answer when 0 is stored in AB, but not when any other value is stored in ABCorrect answer when 0 is stored in AB, but not when any other value is stored in AB

Please let me know any advice. Thank you.

 

Greg

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Tim_Wessman
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You are correct! There is an issue here (I've just put it on the list for correction).

 

Internally, the calcualtor is calling the "fsolve( ) function with arguments like so:

 

fsolve({E1,E2,E3},{F,AB,AC})

 

Give that a try in the CAS and you'll see it return the 3 results. It DOES get those 3 results, but then when it attempts to store them back into AB and AC it doesn't find the internal variables and so doesn't store them.

 

So yes, it is unfortunate and I am kicking myself for this one. I did not have the priveledge of creating the problem 😄 , but it has been there for 6 months and you are the first to find it. 😞

TW

Although I work for the HP calculator group as a head developer of the HP Prime, the views and opinions I post here are my own.

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Tim_Wessman
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The input parser for the home screen/apps needs to know that an item is a variable FIRST before it can use it. Once you have those variables declared/created in some way, they will work as you expect.

 

Here is a thread from just yesterday dealing with this same issue and has more detail:

 

https://h30434.www3.hp.com/t5/Calculators/User-Variables-in-Solve-App/td-p/6583128

 

TW

Although I work for the HP calculator group as a head developer of the HP Prime, the views and opinions I post here are my own.
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Jazzvocation
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The variables are defined in this way (see below). Shouldn't the app know that these are variables if they are in the user variables folder? I did see the post from yesterday regarding the greek letters etc. Please let me know if there is something I am not doing correctly to define the variables ahead of time. But I think I am following the proper procedure.

IMG_3934 copy.jpg

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Jazzvocation
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It seems that the solve app will only solve for one custom variable in one equation at a time. It's incapable of solving a system of equations in custom variables. Hopefully this issue can be resolved somehow. I can obviously solve a  linear system of equations many different ways, so it's not totally crippling to the machine. But it's pretty frustrating nonetheless.

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Tim_Wessman
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You are correct! There is an issue here (I've just put it on the list for correction).

 

Internally, the calcualtor is calling the "fsolve( ) function with arguments like so:

 

fsolve({E1,E2,E3},{F,AB,AC})

 

Give that a try in the CAS and you'll see it return the 3 results. It DOES get those 3 results, but then when it attempts to store them back into AB and AC it doesn't find the internal variables and so doesn't store them.

 

So yes, it is unfortunate and I am kicking myself for this one. I did not have the priveledge of creating the problem 😄 , but it has been there for 6 months and you are the first to find it. 😞

TW

Although I work for the HP calculator group as a head developer of the HP Prime, the views and opinions I post here are my own.

View solution in original post

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Jazzvocation
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I was playing around with the order of the variables and noticed that. Do you think the next firmware update will resolve this? Thanks for letting me know the story! 

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MortenNielsen
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The link refers to this thread... 

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