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+--- Thread: Different behavior of ./ and .* with vectors [SOLVED] (/thread-8268.html)
Different behavior of ./ and .* with vectors [SOLVED] - JMB - 04-29-2017 04:22 PM
When both operands of .* or ./ are vectors of the same dimensions, both functions work accordingly:
[2,4] .* [2,4] → [4,16]
[2,4] ./ [2,4] → [1,1]
But when the first operand is a number they behave in a different way:
4 .* [2,4] → [8,16]
4 ./ [2,4] → Error: Invalid dimension
In this case the operator * (without the dot), also works:
4 * [2,4] → [8,16]
As a workaround for 4 ./ [2,4] one can use:
4 .* [2,4] .^ (-1) → [2,1]
4 * [2,4] .^ (-1) → [2,1]
Is this the intended behavior, or should 4 ./ [2,4] also return [2,1] ?
RE: Different behavior of ./ and .* with vectors - Tim Wessman - 05-01-2017 04:19 PM
Thanks, we'll put it on the list to investigate.
RE: Different behavior of ./ and .* with vectors - JMB - 05-01-2017 05:34 PM
Thank you for your time, Tim!
I have noticed now that 4 ./ [2,4] returns the expected result [2,1] in CAS mode.
RE: Different behavior of ./ and .* with vectors - compsystems - 05-02-2017 09:11 PM
the Hadamard operations (Hadamard Product .*, Hadamard Power .^, Hadamard Inverse .^-1 and Division ./ ) are Element by Element
https://en.wikipedia.org/wiki/Hadamard_product_(matrices)
the two arguments must be an array although the math kernel can expand functionality with scalars
array vs matrix(linear algebra) operations
https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html
HP50 & HPPRIME CAS MODE
hadamard([[1,2],[3,4]],[[3,4],[5,6]]) RETURNS [[3,8],[15,24]] // OK
HP50
hadamard([1,2],[3,4]) RETURNS [3,8] // ok
hadamard([[1,2]],[[3,4]]) RETURNS [[3,8]] // ok
HPPRIME CAS MODE
hadamard([1,2],[3,4]) RETURNS 5*√5 WHY?
hadamard([[1,2]],[[3,4]]) RETURNS [[3,8]]
[1,2] .* [3,4] RETURNS [3,8]
4 ./ [2,4] -> [2,1]
[4] ./ [2,4] -> [2] /!\ Resize to a smaller size
[2,4] ./ [4] -> [1/2]
4 .* ([2,4] .^ -1) -> [2,1]
4./[2,4] -> 4.0 / [2,4] -> 4./[2,4] ?
Without spaces also should operate to each element, as some point operations are equivalent to natural operators like [+] [-] [/]
RE: Different behavior of ./ and .* with vectors - JMB - 02-02-2018 08:44 PM
Corrected in firmware 13333.
Thanks to the HP Prime Team!