when and how to use dot multiplication
165 views (last 30 days)
Show older comments
ok, for my first practice homeowrk, since i have no idea what i am doing in matlab, i was asked to plot the response of a RLC equation that is in the time domain. I got the correct answer, but im not sure what the syntax is doing and if it is needed.
q0=10;R=60;L=9;C=0.0005;
t=linspace(0,0.8)
q=q0*exp(-R*t/(2*L)).*cos(sqrt(1/(L*C)-(R/(2*L))^2)*t);
plot(t,q)
in the equation q, there is the .* operation. Is that even needed if a matrix was not even used? im confused as when to use .* vs *
i know if i had
a=[1 2 3]
b=[5 6 7]
a.*b
would return
5 12 21
but is .* needed in my above q equation?
thanks
0 Comments
Accepted Answer
Voss
on 13 May 2022
"but is .* needed in my above q equation?"
Yes.
t is a vector, and q0, R, L, and C are all scalars.
q0=10;R=60;L=9;C=0.0005; % scalars
t=linspace(0,0.8); % 1-by-100 vector
Consider the expressions to the left and to the right of the .*, which both include t and some scalars:
q0*exp(-R*t/(2*L)) % vector the size of t
cos(sqrt(1/(L*C)-(R/(2*L))^2)*t) % vector the size of t
They are both vectors the size of t, so when you multiply those two vectors, you want to do it element-wise, which is what .* does
q=q0*exp(-R*t/(2*L)).*cos(sqrt(1/(L*C)-(R/(2*L))^2)*t)
giving you another vector the size of t.
9 Comments
Matt J
on 12 Aug 2023
If so, you should Accept-click the answer, and likewise with other valid answers to your posted questions.
More Answers (0)
See Also
Categories
Find more on Parallel Computing Fundamentals in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!