MATLAB: Precise Matrix Power: A^k

linear algebraMATLABnumericsprecision

Hello,

I am currently fighting with (more than) double-precision numerics, with which I am not familiar, so the answer probably lies within this topic. I would like to calculate

with

and

but obviously the precision of

will be bad for big k. Is there a datatype of which I am not aware, or any other trick that will help me? Thanks in advance. 🙂

Best Answer

It will probably be helpfull to use the Symbolic Math Toolbox, and use the tips explained here. For mod(a^b,k) there is a direct function, but for your use case there doesn't seem to exist one.

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What you apparently misunderstand is the idea of operator precedence.

There is a difference between these two operations:

-1^0
ans =
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and

(-1)^0
ans =
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What you need to recognize is that ^ operates before the unary minus operator. Once you recognize that, you recognize it is not a bug, but a design question, and one that makes some sense.

You are not the first person to trip over it though. I've seen this question asked before. :)

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Try:

sympref('default');

Best Answer

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