Error Message: 'Matrix dimensions must agree'

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Tristen Hernandez
Tristen Hernandez 2019-11-2
编辑： Tristen Hernandez 2019-11-2
m%%Declare Variables:
n = [.1, 1.0, 1.5];
t= [0:.1:10];
k = 10 %N/m;
m = 5 %kg;
A = 5; %m (initial postion);
omega0 = sqrt(k/m);
omegad = omega0.*sqrt(1.-n.^2);
s=zeros(1,101);
v=zeros(1,101);
a=zeros(1,101);
s = exp(-n.*omega0.*t).*(A*cos(omegad.*t));
v = -n.*omega0.*exp(-n.*omega0.*t).*(A.*cos(omegad.*t))-exp(-n.*omega0.*t).*(A.*sin(omegad.*t).*omegad);
a = (-n.*omega0).^(2).*exp(-n.*omega0.*t).*(A.*cos(omegad.*t))+exp(-n.*omega0.*t).*(A.*sin(omegad.*t).*omegad)...
+exp(-n.*om
ega0.*t).*(A.*sin(omegad.*t))-exp(-n.*omega0.*t).*(A.*cos(omegad.*t).*omegad);
On line 26 (the s variable) I keep getting the error that the matrix dimensions do not agree and quite frankly I have no idea why, very new to the program and still trying to figure everything out. I appreciate any and all help.
I guess while I'm here I also have a question in that I want A to be a function of s, with it's initial condition being five, so how would I be able to rewrite A in terms of s after the initial run through of it being 5?
The release version is R2019a if that helps with answering.

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采纳的回答

KALYAN ACHARJYA
KALYAN ACHARJYA 2019-11-2
编辑：KALYAN ACHARJYA 2019-11-2
In the following expression
s = exp(-n.*omega0.*t).*(A*cos(omegad.*t));
n have length 3 and t have 101, how can you do element wise vector multiplecation.
As you defined
n =[.1, 1.0, 1.5];
t= [0:.1:10];

更多回答（1 个）

Tristen Hernandez
Tristen Hernandez 2019-11-2
编辑：Tristen Hernandez 2019-11-2
I was able to make the multiplication work by transforming the
t = [0:.1:10]
into
t = [0:.1:10]'
Now I'm trying to put these into a for loop that will use the time in increments of 20, so that I can print the results to a table, it's resulting in an error on line 35
%%Declare Variables:
n = [.1, 1.0, 1.5];
t= [0:.1:10]';
k = 10 %N/m;
m = 5 %kg;
A = 5; %m (initial postion);
omega0 = sqrt(k/m);
omegad = omega0.*sqrt(1.-n.^2);
s=zeros(1,101);
v=zeros(1,101);
a=zeros(1,101);
s = exp(-n.*omega0.*t).*(A*cos(omegad.*t));
v = -n.*omega0.*exp(-n.*omega0.*t).*(A.*cos(omegad.*t))-exp(-n.*omega0.*t).*(A.*sin(omegad.*t).*omegad);
a = (-n.*omega0).^(2).*exp(-n.*omega0.*t).*(A.*cos(omegad.*t))+exp(-n.*omega0.*t).*(A.*sin(omegad.*t).*omegad)...
+exp(-n.*omega0.*t).*(A.*sin(omegad.*t))-exp(-n.*omega0.*t).*(A.*cos(omegad.*t).*omegad);
fprintf("t(s) \t s(m) \t v(m/s) \t a (m/s^2) \t \n");
fprintf("-------------------------------------------------- \n");
for i= [1:20:101]
s(i) = exp(-n.*omega0.*i).*(A*cos(omegad.*i))
v(i) = -n.*omega0.*exp(-n.*omega0.*i).*(A.*cos(omegad.*i))-exp(-n.*omega0.*i).*(A.*sin(omegad.*i).*omegad);
a(i) = (-n.*omega0).^(2).*exp(-n.*omega0.*i).*(A.*cos(omegad.*i))+exp(-n.*omega0.*i).*(A.*sin(omegad.*i).*omegad)...
+exp(-n.*omega0.*i).*(A.*sin(omegad.*i))-exp(-n.*omega0.*i).*(A.*cos(omegad.*i).*omegad);
fprintf("%.4f \n", s(i));
fprintf("%.4f \n", v(i));
fprintf("%.4f \n", a(i));
end
The error reading "Unable to perform assignment because the left and right sides have a different number of elements." The error occurs in line 35.
Quite frankly I have very little idea in what I'm doing in regards to this program so I appreciate all the help. Should I just post this in a new question post?

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