Index exceeds the number of array elements (4).

function [therm,chem,r_c,mfuel,mC02,ddt] = FourStrokeCycle(D,d,rpm,fuel,N)
AirMatrix= readmatrix('AirProperties.xlsx');
pa=101325
Ta=273
sa=3796

cpi= AirMatrix(3,:)
Mi= AirMatrix(2,:)
nin= AirMatrix(1,:)
FuelMatrix= readmatrix('FuelProperties.xlsx');
ReactionMatrix= readmatrix('ReactionRatios.xlsx');

fuel= input("indicate fuel type:",'s');

while  fuel ~= "gasoline" & fuel~="Gasoline" & fuel~="diesel" & fuel~="Diesel"
    fuel= input("Unrecognized entry, indicate fuel type:",'s');
end

switch fuel
    case  {"gasoline","Gasoline"}
        Mf= FuelMatrix(1,1)
        rhof= FuelMatrix(1,2)
        Tai= FuelMatrix(1,3)
        Hf= FuelMatrix(1,4)
        Si= ReactionMatrix(1,:)
        
    case  {"diesel","Diesel"}
        Mf= FuelMatrix(2,1)
        rhof= FuelMatrix(2,2)
        Tai= FuelMatrix(2,3)
        Hf= FuelMatrix(2,4)
        Si= ReactionMatrix(2,:)
end















%test inputs
rpm=1500
d=.02
N=6

V0=0.00006
L=0.1
D=0.02
PhiI=pi/6
PhiE=pi/6
omega= rpm* 0.10472
% convert rpm to omega rad/s

k=[1:1:N+1]
PhiK=(k-1)*(4*pi)/N
tK=(k-1)*(4*pi)/(N*omega)
PhiT= omega.*tK



x=(D/2)*cos(PhiT)+sqrt(((4*L^2)/D^2)-sin(PhiT).^2)
Vt= V0+(pi.*d^2)./4.*(L+(D./2)-x)
r_c= (V0+D*(pi*d^2)/4)/V0


therm = zeros(8,N+1)


P=zeros(1,N+1)
T=zeros(1,N+1)
P(1)=101325


Ru=8.3145
Mbar=Mi*nin(1)/nin
R=Ru/Mbar
m=nin.*Mi
mu=((nin.*Mi)./m)
n(1)=(P(1)*Vt(1))/(R(1)*T(1))
v(1)=Vt(1)/m(1)
c_p=mu(1)*cpi
c_v=c_p-R
for k=1:N
    if PhiK(k)< pi
        P(k+1)=P(k)
        T(k+1)=T(k)
        mu(k+1)=mu(k)
        nin(k+1)=nin(k)
        n(k+1)=n(k)*Vt(k+1)/Vt(k)
        m(k+1)=m(k)*Vt(k+1)/Vt(k)
        v(k+1)=Vt(k+1)/m(k+1)
        
        
    elseif PhiK(k)<2*pi- PhiI 
        
        nin(k+1)=nin(k)
        mu(k+1)=mu(k)
        n(k+1)=n(k)
        m(k+1)=m(k)
        v(k+1)=Vt(k+1)/m(k+1)
        P(k+1)=P(k)*(v(k)/v(k+1))^(c_p/c_v)
        T(k+1)=(P(k+1)*v(k+1))/R
        
    elseif PhiK(k)>=2*pi-PhiI
      if n(k+1)>=0            %ERROR LINE
        CF=(1+10*(rpm-800)/5200)*(r_c-6.854)
        mdot=CF/1000
        ndot=mdot/M
        nin(k+1)=nin(k)+ndot*Si*(tK(k+1)-tK(k))

Index exceeds the number of array elements (4).

Error in test (line 113)

if n(k+1)>=0

[Walter Roberson]

We do not have your data and do not know the answers to the input() statements, so we cannot test your code. Also, you stopped posting in the middle of a if elseif chain, so the code is not complete so we cannot invent our own data to test with.

Answer 1

[Gokul Nath S J]

Hi Carig,

It seems that your code is throwing out an error in the form of incorrect inputs. From the limited information, it seems obvious that the index values of n(k+1) is exeeding the limit it can intake. Further note that variable n can only take 4 array elements and you are accessing a value which is the 5th one. This might be a logical error that would have taken place. Please check for the condition of end of the array by using the length function and input the variable once the verification is passed. A reduced code will looking something like this.

lengthn = length(n);
if k + 1 < n
    if n(k+1) >= 0 
     % code   
    end
end

with regards,

Gokul Nath S