What does the stars in the result of a matrix multiplication mean?

[James Tursa]

We can't run pictures. Please post your code as text and highlight it with the CODE button.

[John D'Errico]

Please don't post a picture of text. As a picture, I cannot copy the matrix A and paste it into MATLAB to explain what you are seeing. Sorry, while it has been said a picure is worth a thousand words, it is worthless here.

You could have far more easily copied the text and pasted it directly into your question.

You might also tell people if you are using MATLAB (and which release) or perhaps some other tool, for example, Octave.

[John D'Errico]

As far as what the stars mean, while MATLAB does not display matrices in that format, what do you know about the adjoint matrix, and the relation of that matrix to the matrix inverse?

What would you expect to see if you multiplied a matrix by its inverse?

And, finally, what is the determinant of the matrix a?

Answer 1

[Steven Lord]

Did you enable the 'rat' display format? From the help text for the format function:

      format RAT     Approximation by ratio of small integers.  Numbers
                     with a large numerator or large denominator are
                     replaced by *.

Since those numbers are extremely small (if you change your display format to 'longg' you'll see they're in the 1e-13 to 1e-15 range) you need a large denominator to write them.