## 284 Reputation

18 years, 263 days

Professor of Economics SUNY Stony Brook I use Maple for Research: To test theoretical modelling ideas with various kinds of general equilibrium deterministic and stochastic models in Macroeconomics and Urban Economics. Graduate classes: In Macroeconomics and Econometric classes. Undergraduate classes: In Urban Economics and Computational Methods classes. Note: You can communicate with me in German and French as well as English.

## LinearAlgebra has problems superseding l...

I kept seeing in the help pages for linalg that it is being superseded by LinearAlgebra, so I have tried to work with LinearAlgebra. However, it turns out that LinearAlgebra is very clumsy and annoying for symbolic computations. LinearAlgebra was clear meant to be a numerical calculation package. Unfortunately, the desiderata for numerical calculations are not the same as for symbolic calculations. The main feature of LinearAlgebra which causes this clumsiness is the requirement that all elements of a Matrix be defined. To do symbolic calculations this means assigning a symbol to use with an index for the undefined elements of the Matrix. The name of this symbol has to be different from that of the Matrix itself, and the indexed symbol is not an array or a table or a Matrix. Already then you have two names for essentially the same thing. ==> First Problem. Now, lets say you do some calculations with these Matrices and end up with expressions that that contain the indexed symbolic names. To assign other values to these indexed symbolic names in the resulting expressions, you have to assign the indexed symbolic names new values and you cannot use matrix operations for that since these indexed symbolic names are not arrays or Matrices or even tables. ==> Second Problem. Now if you want to unassign the symbolic names again or assign new values and have these values show up in the original Matrices, you have to reassign the symbolic names and reassign the values in the original Matrices. (Matrix elements cannot be unassigned.) In other words, do the job twice. ==> Third Problem.

## Edit|Remove Output|From Selection Stoppe...

It seems that Edit|Remove Output|From Selection just stopped working. Any ideas what happened? I don't know of any option that affects this that I could have changed unknowingly. However, From Worksheet works fine. I am working in standard worksheet mode with either 2D or 1D math input.

## How does one revert to Worksheet mode af...

If the last entity in a worksheet is a Document Block, I can find no way to get a Worksheet execution group and prompt AFTER that Document Block. Have I missed something? I've searched all through the help system and forums with no luck. Of course, one could have had more foresight and have put the Document Block BEFORE a final Worksheet prompt. However, one would have hoped that, since there is a command to Creat Domument Block, theere would be a command to Exit Document Block. Using Insert Execution Group just puts the execution group into the Deocument Block. When caught in this predicament, the only way I could see to get out was to Remove the DB, put in an extra execution group at the end, and then recreate the DB without the last execution group.

## Maple shuts down when a 3d plot is left ...

Maple shuts down when a 3d plot is left clicked. It produces an error log file which says: An unexpected exception has been detected in native code outside the VM. Unexpected Signal : EXCEPTION_ACCESS_VIOLATION (0xc0000005) occurred at PC=0x692287D5 Function=atiPPHSN+0x187535 Library=C:\WINDOWS\system32\atioglxx.dll My ATI video cards are both (there seem to be both a primary and secondary) RADEON X800 XT Driver: ati2mtag.sys Wednesday, August 25, 2004 I'm not sure if I've done a 3d plot on this machine since I installed Maple 10 (and since updated to 10.03). But this has never happened before.
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