Error: Matrix dimensions must agree

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

 采纳的回答

James Tursa
James Tursa 2019-9-21
编辑:James Tursa 2019-9-21
You could use V(2:end) or V(1:end-1) instead of V in that line. Or maybe average the two.

5 个评论

Thank you, this works! I realized with your anwer that I should use V(1:end-1) throught all my equations.
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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