How to assign an element of a column array to a variable?

Sorry if this might seem silly, but I am not able to get this: I have :

d0=rand(Nn,1);
M=2+2*rand(Nn,1);
NN=2+2*rand(Nn,1);
RR=0.35+0.25*rand(Nn,1);
d=zeros(Nn,1);
ni=zeros(Nn,1);
for i=1:Nn
 D0=d0(i,1);
 r=RR(i,1);
 n=NN(i,1);
 m=M(i,1);
 D=1-power(power(1-D0,n+1)-((N-N0)/Nc).*(n+1).*power((1-r/R1),m),1./(n+1));
 d(i,1)=D;
end

gives:

Subscript indices must either be real positive integers or logicals.

Error in constant_loading_1 (line 3) D0=d0(i,1);

[David Young]

I copied your code and ran it and I don't get the error - is what you're running exactly what you've shown here?

[Adam]

Looks fine to me though is that exactly the code that gave the error? It is pointing to a line3, but the code it shows as causing the problem is not the 3rd line of that code.

[Sri]

Nn=input('Number of samples: ');
M=2+2*rand(Nn,1);
NN=2+2*rand(Nn,1);
RR=0.35+0.25*rand(Nn,1);
d0=rand(Nn,1);
Ns=input('Specified Number of cycles: ');
count=0;
d=zeros(Nn,1);
ni=zeros(Nn,1);
for i=1:Nn
    [D(i),Ni(i)]=initiation_1( d0,N,N0,Nc,R1,RR,M,NN )
end

function [ D,Ni ] = initiation_1 (d0,N,N0,Nc,R1,RR,M,NN)
loading=input('Is the loading amplitude constant?(Y/N)[Enter / to termiante]: ','s');
if (loading=='Y')||(loading=='y')
 [D,Ni]=constant_loading_1(d0,N0,Nc,R1,RR,NN,M,N);
    d(i,1)=D;
    ni(i,1)=Ni;

function [ D,Ni ] = constant_loading_1(d0,N0,Nc,R1,RR,NN,M,N)
D0=d0(i,1);
r=RR(i,1);
n=NN(i,1);
m=M(i,1);
D=1-power(power(1-D0,n+1)-((N-N0)/Nc).*(n+1).*power((1-r/R1),m),1./(n+1));
Ni=ceil(N0+((Nc/(n+1)).*(power(1-D0,n+1)).*(power(R1/(R1-r),m))));
end

[Sri]

The values in the column vectors d0,M,NN,RR and D0,m,n,r are different. Why is this happening?

[Adam]

You are assigning new random data to each of them. If you want the same data just define the others in terms of the first one you assign.

You can setup random seed I think to ensure each call to rand starts from the same seed and would thus give the same sequence for a given length, but for your case that seems overboard and the above method would be far easier.

Answer 1

[David Young]

The variable i is not given a value in initiation_1. That means that it gets its default value, which is the square root of -1. Hence the error. A solution is to pass the value of i as an argument to the function.

In general, it is good practice to avoid using i and j as the names of ordinary variables, because of the possibility of obscure errors like this. You could use ii and jj instead, for example.