Why don't these matrix dimensions agree?

Nlayers=20;                     %number of layers in the lung
z=(1:Nlayers);

TLC=7;                          %total lung capacity
Htot=0.16;                      %total lung height, metres
plung=300;                      %lung density kg/m3
Vad=0.15;                       %Volume of the anatomical dead space
g=9.81;                         %Gravitational acceleration

Fs=64;
dt=1/Fs;
StopTime=8;
t=(0:dt:StopTime-dt);

Nalvtot=300;
Nalvz=Nalvtot/Nlayers;          %Number of alveoli in a layer
r=(0.00009)*sin(1.57*t)+(0.00013); %alveolar radius
Valvz=(4/3)*pi*r.^3;             %volume of the alveolus
Vtotal=Vad+Nalvz*Valvz*20;

Pcw=0.71-((0.95*TLC)/((Vtotal/TLC)-(0.22*TLC))-1)*0.58;   %Pressure component of the chest wall

When i run this it says

"Error using  / 
Matrix dimensions must agree.

Error in Pcw_stripped (line 21)
Pcw=0.71-((0.95*TLC)/((Vtotal/TLC)-(0.22*TLC))-1)*0.58;   %Pressure component of the chest wall

Error in run (line 63)
evalin('caller', [script ';']);"
But I'm sure why? Help!

Answer 1

[Star Strider]

You need to vectorise that line, doing element-wise operations. In this instance, that means replacing (/) with (./).

See if this improves your code:

Pcw=0.71-((0.95*TLC)./((Vtotal./TLC)-(0.22*TLC))-1)*0.58;   %Pressure component of the chest wall