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Error: Matrix dimensions must agree

Asked by Jose Cruz on 21 Sep 2019
Latest activity Commented on by Jose Cruz on 21 Sep 2019
I need to multiply the Diff () = dVdt [1369 x 1] with V [1370 x 1] equation. How can I add to the lenght of dVdt? I need to add three terms together and their Matrix Dimeions must match. See error below:
Matrix dimensions must agree.
Error in homework_1_P2 (line 40)
Inertia = (1.1*Mv*(dVdt).*V)./1000; % kW
load CYC_FUDS.mat
t = cyc_mph(:,1); % Time [s]
Vmph = cyc_mph(:,2); % Velocity [mph]
V = Vmph.*(1609/3600); % Velocity [m/s]
dVdt = (diff(V)./diff(t)); % Accel. m/s^2
% Aerodynamic = (0.5*pa*Cd*Af*V.^3)./1000; % kW
% Rolling = ((Cr*Mv*g*cos(Xa)).*V)./1000; % kW
Inertia = (1.1*Mv*(dVdt).*V)./1000; % kW
% Pw = (Aerodynamic+Rolling+Inertia); % kW

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1 Answer

Answer by James Tursa
on 21 Sep 2019
Edited by James Tursa
on 21 Sep 2019
 Accepted Answer

You could use V(2:end) or V(1:end-1) instead of V in that line. Or maybe average the two.

  5 Comments

Is gradient meant to be used with funtions or will it work with numerical (emperical) values loaded from .mat?
There are two versions of gradient(). One of them works with symbolic functions or symbolic expressions; the other works with numeric matrices.
Thank you! I'll have to try with the gradient and see how it compares to using V(1:end-1).

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