# Matrix to Scalar Problem

1 view (last 30 days)
Nahuel on 6 Sep 2023
Commented: MarKf on 6 Sep 2023
Hi everyone,
I have a problem in the line 10, that it is ofcourse cause of the multiplication between a Matrix and a Scalar. But I do not find how to solve it.
1. t=0:3:60;%seconds
2. Pos0=0;%position
3. Vel0=0;%velocity
4. W=6.28;%frecuency
5. e=2.71828;%Euler
6. Damp_Coef=0;
7. Wd=W*(1-Damp_Coef^2)^0.5;
8. alfa=atan((Vel0+Pos0*Damp_Coef*W)/(Wd*Pos0));
9. C=(Pos0^2+((Vel0+Pos0*Damp_Coef*W)^2)/Wd^0.5)^(0.5);
10. x=C*e^(-Damp_Coef*W*t)*cos(Wd*t-alfa);
11. figure
12. plot(t,x)
13. xlabel('time,s')
14. ylabel('x(t)')
15. legend('NANU')
16. title('lets see')
John D'Errico on 6 Sep 2023
Edited: John D'Errico on 6 Sep 2023
Please don't number those lines. That makes it impossible to copy your code. Why do you want to make it more difficult to get help? Just making the line in question bold faced as you did was certainly sufficient.
MarKf on 6 Sep 2023
fortuantely it is just a numbered list, so it is easy to copy actually... but yes interesting appoach, bold/underlined or even code %<-- issue here would have worked

Les Beckham on 6 Sep 2023
t=0:3:60;%seconds
Pos0=1;%position <<< Pos0 can't be zero since you divide by Wd*Pos0 when calculating alfa
Vel0=0;%velocity
W=6.28;%frecuency
e=2.71828;%Euler
Damp_Coef=0.02; % <<< Damp_Coef can't be zero
Wd=W*(1-Damp_Coef^2)^0.5;
alfa=atan((Vel0+Pos0*Damp_Coef*W)/(Wd*Pos0));
C=(Pos0^2+((Vel0+Pos0*Damp_Coef*W)^2)/Wd^0.5)^(0.5);
x=C*exp(-Damp_Coef*W.*t).*cos(Wd.*t-alfa);
% ^ use exp instead of e^ and use element-wise multiplies: .* instead of *
figure
plot(t,x)
grid on
xlabel('time,s')
ylabel('x(t)')
legend('NANU')
title('lets see')

Torsten on 6 Sep 2023
x=C*exp(-Damp_Coef*W*t).*cos(Wd*t-alfa);

MarKf on 6 Sep 2023
Use a dot "." before an element-wise operation, that is also to multiply, divide, raise etc a scalar value to each of the element of a vector/matrix. Example below, tho not sure that's what you meant to do.
t=0:3:60;%seconds
Pos0=0;%position
Vel0=0;%velocity
W=6.28;%frecuency
e=2.71828;%Euler
Damp_Coef=0;
Wd=W*(1-Damp_Coef^2)^0.5;
alfa=atan((Vel0+Pos0*Damp_Coef*W)/(Wd*Pos0));
C=(Pos0^2+((Vel0+Pos0*Damp_Coef*W)^2)/Wd^0.5)^(0.5);
x=C*e.^(-Damp_Coef*W*t).*cos(Wd*t-alfa);
figure
plot(t,x)
xlabel('time,s')
ylabel('x(t)')
legend('NANU')
title('lets see')

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