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# HP Prime: Advanced Graphing with complex equations doesn't work?

07-21-2014 06:00 AM

I have been experimenting with the Advance Graphing app, using equations involving complex numbers, but I can't get them to work.

E.g. Start the Advanced Graphing app, enter the single equation '|(X,Y)|<2', and set the X and Y range to something which makes sense, e.g. X from -4 to 4 and Y from -3 to 3.

My Prime shows the equation as '|X+Y*i|<2'.

The Num: table shows appropriate true och false values in the V1 column, but the Plot: just shows "Error: Invalid object".

Further experimentation seems to indicate I get this error just because "i" is used. Replacing "i" with the sqrt(-1) produces no errors but no plot either.

Changing the equation to the equivalent 'sqrt(X^2+Y^2)<2' produces the plot I expect, a solid circle with radius 2.

I this a bug or a setting I must enable somewhere? As it is now, I'm apparently unable to use any complex arthmetic inside a plot equation.

My Prime software version is "2014 3 31 (6030)"

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## HP Prime: Advanced Graphing with complex equations doesn't work?

08-29-2014 12:15 AM - edited 08-29-2014 12:16 AM

I also tried putting an RE around the left side of the equation, but it didn't change anything. As soon as i appears in the equation, trying to plot it gives the "Error: Invalid object" message.

Edit: Same firmware version, 6013

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## HP Prime: Advanced Graphing with complex equations doesn't work?

08-29-2014 12:50 AM

I've found an explanation: http://www.hpmuseum.org/forum/thread-176.html

To summarize: The Advanced Graphing plot *does not* simply evaluate the given equation at discrete points. Instead, it relies on "interval arithmetic" to deduce where the plot will change from true to false (or vice versa). This is the reason why the Advanced Graphing executes so quickly.

The truth table *does* evaluate at discrete points. However, there doesn't seem to be any way of producing a plot from the table.

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