How to store an initial value in an array. x should start at 0 and y should start at 1. The step size is 0.25. I do not know how to store my initial x and y values in the array.

clear;clc

syms x
syms y
f(x,y)= (1+2*x)*sqrt(y)
h = 0.25;
x_array = zeros(1,5);    %array of x
y_array = zeros(1,5);    %array of y
fprintf('Step 0: x = %6.2f, y = %6.2f\n', x, y);
for i=1:5
k1 = h*f(x,y);
k2 = h*f(x+h/2, y+k1/2);
k3 = h*f(x+h/2, y+k2/2);
k4 = h*f(x+h, y+k3);
y = y + (k1+2*k2+2*k3+k4)/6;
x = x + h;
fprintf('Step %d: x = %6.4f, y = %18.15f\n', i, x, y);
end
x_array(i+1) = x
y_array(i+1) = y

[Alan Moses]

Do you wish to start your iterations with the initial values -> x=0 and y=1 ? You may try the following code:

clear;clc
syms x
syms y
f(x,y)= (1+2*x)*sqrt(y);
h = 0.25;

x0 = 0; %Initial value of x
y0 = 1; %Initial value of y

x_array = zeros(1,6);    %array of x
y_array = zeros(1,6);    %array of y

%Storing initial values in the array
x_array(1) = x0; 
y_array(1) = y0;

fprintf('Step 0: x = %6.2f, y = %6.2f\n', x0, y0);
for i=1:5
    k1 = h*f(x0,y0);
    k2 = h*f(x0+h/2, y0+k1/2);
    k3 = h*f(x0+h/2, y0+k2/2);
    k4 = h*f(x0+h, y0+k3);
    y0 = y0 + (k1+2*k2+2*k3+k4)/6;
    x0 = x0 + h;
    fprintf('Step %d: x = %6.4f, y = %18.15f\n', i, x0, y0);
    x_array(i+1) = x0;
    y_array(i+1) = y0;
end

Answer 1

[Cris LaPierre]

I suggest Chs 4, 5 and 13 of MATLAB Onramp (vectors and arrays, indexing and modifying arrays, and for loops)