Re: subtraction of vectors results in 0 [bug?]

[Nicholas Jankowski]

On Mon, Nov 30, 2015 at 9:50 AM, Jonathan Camilleri <address@hidden> wrote:

I am not sure if this is correct.

v

v =

   1   0

   1   1

   2   4

>> x

x =

   1   0

   1   1

   2   4

>> ans = v-x

ans =

   0   0

   0   0

   0   0

error: operator *: nonconformant arguments (op1 is 3x2, op2 is 3x2)

See http://www.purplemath.com/modules/mtrxadd.htm.

I do not have access to the bug tracker.

--

Jonathan Camilleri

Mobile (MT): ++356 7982 7113
E-mail: address@hidden
Please consider your environmental responsibility before printing this e-mail.
 

no bug.  this is how vector/matrix addition and subtraction is supposed to work. v(i,j) - x(i,j) = ans(i,j)

more of an issue is how you got a nonconformant argument error.  You didn't show any usage of the * operator to create that error message.  it looks like the error you should get if you tried:

>> x*v

error: operator *: nonconformant arguments (op1 is 3x2, op2 is 3x2)

because * is for matrix multiplication, which has very specific size requirements. See:
https://en.wikipedia.org/wiki/Matrix_multiplication

If you want to multiply the elements, you have to use the element-wise multiplication operator .*

>> x.*v
ans =

    1    0
    1    1
    4   16