It shows me that a vector multiplied by a matrix is not the same as a matrix multiplied by a vector. Dang, so simple....
Thank you so very much...
Tim
Hi Tim,
I did exactly what is in my reply.
Set m to {{11, 1}, {0, -6}}
m
{{11, 1}, {0, -6}}
m = {{11, 1}, {0, -6}};
Take the dot product of m with {-4, 2}
{-4, 2}
m.{-4, 2}
Do you not get the right answer if you copy and paste those two lines into a notebook and evaluate them?
Rohit, Can you explain what you did to get the correct answer? Have I not gone far enough in the tutorial? Learning curve on this is quite steep at 65....
m = {{11, 1}, {0, -6}}; m.{-4, 2} (* {-42, -12} *)
Did I put in the wrong order? I should use matrix multiplied by vector instead? Gotta run back upstairs now and try that...
Whew!
That was it.....
Now if I multiply that by vector a which is (-4,2) I get a result of {-44, -16}, the correct answer is {-42, -12} and I don't understand why I get the wrong one.....
I even worked it by hand to make sure the indicated correct answer is indeed the correct answer. That is using the dot operator. I've literally been looking at this for weeks.
Hi Timothy,
Not sure which tutorial you were following, this one has several examples of matrix and vector multiplication.
Yes, that is the one I have been going over multiple times.
Now can you take a look at my other response of why the wrong answer comes out when I use the vector with a dot operator times the matrix?
MatrixForm {m} means "multiply MatrixForm by a list containing m.
MatrixForm {m}
MatrixForm
You probably intended MatrixForm[m].
MatrixForm[m]
