Display Error when using the Advantage Pac (.mod) with MATRX, SE function and MEDIT of MATRX

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ratwolf
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Joined: Fri Feb 12, 2021 1:00 am

Display Error when using the Advantage Pac (.mod) with MATRX, SE function and MEDIT of MATRX

Post by ratwolf »

When solving linear equation systems with the help of the MATRX and SE function of the Advantage Pac everything works fine. Ater entering the values for MAT A, MAT B, executing SE and recalling MAT B again, the expected results are displayed in MAT B. But after recalling again the elements of MAT A I always get strange displays for some elements.

Concrete example: Entering a 4x4 matrix (real numbers), see highlighted in screen shot. Coefficients for current and resistance in MAT A, Coeeficents for Voltage in MAT B.

After executing SE and again recalling the elements of MAT A (MEDIT). I always get strange displays for elements 4.3 and 4.4 of MAT A, see screenshots.
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Screenshot 2021-09-19 at 09.50.51.jpg
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ratwolf
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Re: Display Error when using the Advantage Pac (.mod) with MATRX, SE function and MEDIT of MATRX

Post by ratwolf »

happens exactely and reproducable as well with other emulators such as 41CX for Android...

but not with the Matrix function of the HP42s respectively DM42 where there is a MAT A, MAT B and MAT X 😁
dlachieze
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Location: France

Re: Display Error when using the Advantage Pac (.mod) with MATRX, SE function and MEDIT of MATRX

Post by dlachieze »

ratwolf wrote:
Sun Sep 19, 2021 10:40 am
After executing SE and again recalling the elements of MAT A (MEDIT). I always get strange displays for elements 4.3 and 4.4 of MAT A, see screenshots.
I got the same display by testing your exemple with the HP Advantage module in my 41CX, the reason is given in the Advantage manual: after executing SE, the matrix A is in its LU-decomposed form.
Alteration of the Original Matrix.
The input matrix A is altered by the operations finding the inverse, the determinant, the transpose, and the solution of the matrix equation. You can re-invert A - and re-transpose AT to restore the original form of A. However, if you have calculated the determinant or the solution matrix, then A is in its LU-decomposed form. To restore A, simply invert it twice. The LU-decomposition does not interfere with any subsequent MATRX operation except transposition and editing*.
Editing and Viewing an LU-Decomposed Matrix.
LU-decomposed matrices are stored in a different form than normal matrices:
• Certain elements contain alpha data.
• The matrix status register is modified to indicate that the matrix is in LU form.
So it's not a display error, this is just the way the HP Advantage module handles the resolution of systems of equations.
DM42: 00425 - DM41X: β00066
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ratwolf
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Re: Display Error when using the Advantage Pac (.mod) with MATRX, SE function and MEDIT of MATRX

Post by ratwolf »

Thanks for prompt reply!
Guess I read this before as well but did not connect this to the described display issue. Cheers! :mrgreen:
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