I keep getting the error index exceeds the number of array elements(1)

roll = zeros(1,300);

for i = 1:300
    dice = 1 + ceil(11*rand(1));
end
freeornah = roll+dice(i)

freeornah = roll+dice(i)I keep getting the error index exceeds the number of array elements(1). I am trying to add each number in the column vector roll with each dice roll. Then I'm trying to create a logical where if the number I receive for freeornah is true if it is either 11 or 12.

[Stephen23]

"freeornah = roll+dice(i)I keep getting the error index exceeds the number of array elements(1)."

The reason for that is simple: your completely overwrite dice on every loop iteration, so at the end you have only the scalar value from the final iteration. Then you try to access the 300th element of a scalar array -> error!

"I am trying to add each number in the column vector roll with each dice roll."

Given that roll consists only of zeros then you can ignore it and just add the numbers in dice. Note that roll is not a column vector, it is a row vector. From your description and buggy code it is not very clear what you are trying to achieve. Perhaps a simple example would help, with example input and output arrays.

"Then I'm trying to create a logical where if the number I receive for freeornah is true if it is either 11 or 12."

Use > or ==

[Brian Peoples]

I editted the code and it seems I am able to get a 1 or a 0 for each roll of an 11 or a 12 by using a logical. I was wondering how I would get a percentage of each true logical (aka each free food item) out of 300.

My new code is:

roll = zeros(1,300);

for i = 1:300
    roll = zeros(i);
    dice = 1 + ceil(11*rand(i));
    freeornah = roll(i)+dice(i);
    free = logical(freeornah(freeornah>10))
    %percent = free(i)/300    (here is where i'm getting stuck!!)
end

Answer 1

[Satoshi Kobayashi]

The problem is that dice is completely changed in each loop.

In this case, roll is meaningless.

dice = zeros(1,300);
for i = 1:300
    dice(i) = 1 + ceil(11*rand(1));
end
freeornah = dice==11|dice==12;

Answer 2

[Dhruvi Upendra]

clc clear all
f=@(x,y,z) z; g=@(x,y,z) (x^2+6*x-9)/75; fex=@(x) (12*x^3-54*x^2-x^4)/900;
a=0; b=3; h=0.1; n=30;
y=0; z=0; i=0; for x=a:h:b i=i+1;
    k1=f(x,y(i),z(i));
    l1=g(x,y(i),z(i));
    k2=f(x+0.5*h,y(i)+0.5*k1,z(i)+0.5*l1);
    l2=g(x+0.5*h,y(i)+0.5*k1,z(i)+0.5*l1);
    k3=f(x+0.5*h,y(i)+0.5*k2,z(i)+0.5*l2);
    l3=g(x+0.5*h,y(i)+0.5*k2,z(i));
    k4=f(x+h,y(i)+k3,z(i)+l3);
    l4=g(x+h,y(i)+k3,z(i)+l3);
    y(i+1)=y(i)+(k1+2*k2+2*k3+k4)*h/6;
    FF(i)=fex(x);
    xx(i)=x;
end
plot(xx,y(1:n+1),'o',xx,FF)
legend('RK4','Exact solution')
grid on
xlabel('X')
ylabel('Y')
title('RK4 vs Exact solution')

I have written Matlab code for Runge Kutta fourth order method for second order differential but I'm getting this error I don't know how to solve it !

[Walter Roberson]

This is unrelated to the user's Question and should be created as its own Question, with a clear indication of what the error message is and which line it is occuring on.