decimal increment inside a for loop

Hi, I am trying to run a for loop as part of my code. I am trying to have 15 j values between z2 and z1 which are decimal numbers and change with every iteration. The error I am getting is "Subscript indices must either be real positive integers or logicals."I know I am getting the increments wrong but need some suggestions to solve the error.

    for i = 1:1:49
        X_even = [];
        C_even = [];
        P_even = [];
        z1 = S0 - 2 * std(S) * sqrt(T - dt);
        z2 = S0 + 2 * std(S) * sqrt(T - dt);
        z = (z2-z1);

        for j = z1:(z2-z1)/15:z2

            X_even = [X_even ; X1(j,i)];
            C_even = [C_even ; C1(j,i)];
            P_even = [P_even ; P1(j,i)];
        end

       X1_even = [X1_even X_even];
       C1_even = [C1_even C_even];
       P1_even = [P1_even P_even];
    end

Answer 1

[Star Strider]

You need to do something like this:

          vj = z1:(z2-z1)/15:z2;
          for j = 1:length(vj)
              X_even = [X_even ; X1(j,i)];
              C_even = [C_even ; C1(j,i)];
              P_even = [P_even ; P1(j,i)];
          end

If you are using ‘vj’ in calculations (although you do not seem to be in the code you posted), refer to fractional ‘j’ as ‘vj(j)’.

[A Basu]

Thanks a lot!

[Star Strider]

As always, my pleasure!

[Pablo Tejada Jr.]

Mr. Strider If I may ask a similar question. I created a "for Loop" that worked up to the point where I tried to modify within the "For Loop". If I may I am going to post my code. My error begins on my third for loop when I add .1 to my stress0.

formula Im using if it helps explain my question.

clc
clear all
close all

E1=4000; 
E2=5000; 
Mu= 1.2*10^5; 
stress0.norm = 800;

%The Following values are used to answer part E I
stress0.plus10  = 800+.1;  
stress0.minus10  = 800-.1;

% The following loop generates points with E1 and E2. 

for i=1:stress0.norm 
    strain.normal(i)=i/E1; 
    strain.E1plus10(i)=i/(E1+.1); 
    strain.E1minus10(i)=i/(E1-.1); 
    strain.E2plus10(i)=i/E1; 
    strain.E2minus10(i)=i/E1; 
end

for i=stress0.norm:1500  
    strain.normal(i)=(i/E1)+((i-stress0.norm)/E2); 
    strain.E1plus10(i)=(i/E1+.1)+((i-stress0.norm)/E2); 
    strain.E1minus10(i)=(i/E1-.1)+((i-stress0.norm)/E2); 
    strain.E2plus10(i)=(i/E1)+((i-stress0.norm)/(E2+.1));
    strain.E2minus10(i)=(i/E1)+((i-stress0.norm)/(E2-.1));
end


% Creating a another seperated loop for changes in stress0


for i=1:stress0.plus10
    strain.stress0plus10(i)=i/E1; % This is where my error begins
end

for i=stress0.plus10;1500
    strain.stressplus10(i)=(i/E1)+((i-stress0.plus10)/E2); % This is where my error begins
end

[Steven Lord]

There's no such thing as element 799.9 of an array, like you're trying to assign to in this for loop.

for i=stress0.plus10;1500
    strain.stressplus10(i)=(i/E1)+((i-stress0.plus10)/E2); % This is where my error begins
end

The semicolon in the line with your for loop should probably be a colon, but that won't save you because the first iteration through the loop you're trying to assign to strain.stressplus10(799.9).

[Star Strider]

Als, that should be a new Question. It has nothing directly to do with the current thread.