multiply a matrix by a specific value from a vector
显示 更早的评论
Hi : I want to multiply a matrix (resultx) sized 10001x10001 by only one value from etae which is sized 1x50.I want to access only the first value of etae and the last value of eate separately. can I do it like this:
Iph1=pinc*(resultx).^2*(etae(1,1))/h*v) % for first value
and,
Iph2=pinc*(resultx).^2*(etae(1,50))/h*v) % for last value
and, did I square (resultx) correctly?. should the (.) be there?. pinc,h, v, etae are single values. resultx is (mXn)
2 个评论
James Tursa
2015-4-8
What are the sizes of pinc, h, and v? Scalars? As written, only h is in the denominator. Is this what you want or do you want v there as well?
采纳的回答
Jeffrey Girard
2015-4-8
编辑：Jeffrey Girard
2015-4-8
Let's use a cleaner example:
a = 5;
b = [1,2,3,4;5,6,7,8];
c = [0.5,1.0,1.5,2.0];
So if I want to multiply the matrix b by scalar a and then add that product's square to the first value of vector c, you should do the following:
d = (b .* a) .^ 2 + c(1);
And if you want to do the same but with the last value of vector c , you should do the following:
d = (b .* a) .^ 2 + c(end);
The dot before a mathematical operator (e.g., .*) indicates that you want to perform the operation using array operations (or element-wise) rather than matrix operations. If you are unfamiliar with matrix algebra, you want to be using the dots (i.e., array operations). In some cases, such as when using scalars, the two are equivalent, but it will be safer for you to use the dots as I did above.
更多回答（0 个）
类别
在 帮助中心 和 File Exchange 中查找有关 Logical 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
