When do you write the vector in a row or column... our book/ teacher seems to jump back and forth...

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- October 19th 2009, 08:46 AM #1

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- October 19th 2009, 12:41 PM #2

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It is pretty arbitrary but sometimes it is VERY important which one's used. For example, a row vector with n components can been seen as a 1 x n matrix, and the same column vector as a n x 1 matrix ==> you can matrix multiply the former by the latter (in this exact order!), but NOT the other way around unless n = 1.

Don't worry, you'll see this later on.

Tonio

- October 19th 2009, 03:30 PM #3

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- October 19th 2009, 04:16 PM #4

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- October 19th 2009, 04:43 PM #5

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- October 19th 2009, 09:28 PM #6

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- October 20th 2009, 09:59 AM #7

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- October 20th 2009, 12:56 PM #8

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- October 20th 2009, 05:12 PM #9

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- October 20th 2009, 06:05 PM #10

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When you say solve systems of equations you mean Gauss or

Gauss-Jordan reduction, right?

Then you operate on rows, and your aim is to set the system in row-echelon form.

You could although in theory write everything as columns, but it would be

awkward to write an equation like "x+y=4" on it's side.

Now for spans and general vectors it doesn't really matter which way you write it.

The reason you write spans usually with column vectors is that they look

nicer side by side than row vectors (and you will see another reason when working with

linear maps as matrixes) . It is just convention to write it

as column vectors.

Like tonio said before the determinant of a matrix is independant of wether

you write the vectors as columns or vectors.

Your calculus book probarbly writes vectors like rows because you are

used to working with cordinates (x,y) before.

So my point is it really doesn't matter, don't waste too much time thinking about

whether to write rows- or columns . Try to focus on other more important things in

your linear-algebra class.

Hjörtur

- October 20th 2009, 06:24 PM #11

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