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

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Brian Peoples on 2 Feb 2019
Commented: Walter Roberson on 2 Dec 2019
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.
##### 2 CommentsShowHide 1 older comment
Brian Peoples on 2 Feb 2019
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

Satoshi Kobayashi on 2 Feb 2019
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;

Dhruvi Upendra on 2 Dec 2019
Edited: Walter Roberson on 2 Dec 2019
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 on 2 Dec 2019
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.