HP Forum Archive 21

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Absolute Value and Matrix Message #1 Posted by BruceTTT on 4 Nov 2013, 11:51 p.m. What does the absolute value do to a matrix argument? For a 2x2 identity matrix it returns the square root of 2. For [[2,0][0,2]] it returns 2 root 2.

Re: Absolute Value and Matrix Message #2 Posted by Paul Dale on 5 Nov 2013, 12:01 a.m., in response to message #1 by BruceTTT Frobenius norm perhaps? Most likely one of the matrix norms. - Pauli

Re: Absolute Value and Matrix Message #3 Posted by Michael de Estrada on 5 Nov 2013, 12:04 a.m., in response to message #1 by BruceTTT That's because it returns the Frobenius (Euclidean) norm of the matrix array, which is the square root of the sum of the squares of the matrix elements. So for a 2x2 identity matrix it's sqrt (1^2+1^2) = sqrt (2). In the special case of a 2D or 3D vector, the absolute value is interpreted as the magnitude or length of the vector. Edited: 5 Nov 2013, 12:12 a.m.

Re: Absolute Value and Matrix Message #4 Posted by BruceTTT on 11 Nov 2013, 7:55 p.m., in response to message #3 by Michael de Estrada OK, thanks. Do you mean a 1D vector that || interprets as the norm? I see that [3 4] || returns 5. Also, is there a LIST-> function?

Re: Absolute Value and Matrix Message #5 Posted by Michael de Estrada on 11 Nov 2013, 8:19 p.m., in response to message #4 by BruceTTT I meant a vector in 2D or 3D space, where the values are the coordinates. So it's a 1x2 or 1x3 matrix, which is commonly referred to as a vector. Regardless, it is the SRSS (square-root-of-the-sum-of-the-squares). As to your second question I'm not sure what you are asking.

Re: Absolute Value and Matrix Message #6 Posted by Walter B on 11 Nov 2013, 11:52 p.m., in response to message #4 by BruceTTT Quote: Do you mean a 1D vector that || interprets as the norm? A 1xn or nx1 matrix is called a vector (of dimension n>1). FYI, a '1D vector' is a (scalar) number. d:-)

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