Making a Euler Method script to solve for velocity but am encountering "Array indices must be positive integers or logical values" Error

%Script for Euler Method to numerically solve the

%velocity of a skydiver modeled as a smooth sphere

clc;

close all;

clear;

m = 70.0; % Mass in kg

D = 0.47; % Drag Coefficent

R = 0.5; % Radius of Sphere in m

p = 1.225; % Density of air in kg/m^3

A = 0.79; % Fronal area in direction of travel in m^2

g = 9.81; % Gravity in m/s^2

h = 3; % Time step Size

t = 0:h:9; % the range of t

v = zeros(size(t)); % allocate the result v

v(1)=0; % Inital condition of velocity

for t=0:3:9

f = (g - (D * p * A * v.^2)/(2*m));

v(t+1) = v(t) + h * f;

end

Array indices must be positive integers or logical values.

Error in Untitled3 (line 22)

v(t+1) = v(t) + h * f;

Answer 1

[Alan Stevens]

Try changing your loop to

for i=1:numel(t)   %%% i loop not t
    f = (g - (D * p * A * v(i).^2)/(2*m)); %%% v(i)
    v(i+1) = v(i) + h * f;  %  i not t
end

[Mathieu NOE]

almost there !

the for loop must be stopped 1 index earlier to have t and v the same length

clc;
close all;
clear;
m = 70.0; % Mass in kg
D = 0.47; % Drag Coefficent
R = 0.5; % Radius of Sphere in m
p = 1.225; % Density of air in kg/m^3
A = 0.79; % Fronal area in direction of travel in m^2
g = 9.81; % Gravity in m/s^2
h = 1; % Time step Size
t = 0:h:9;  % the range of t
v = zeros(size(t));  % allocate the result v
v(1)=0; % Inital condition of velocity

for i=1:numel(t)-1   %%% i loop not t
    f = (g - (D * p * A * v(i).^2)/(2*m)); %%% v(i)
    v(i+1) = v(i) + h * f;  %  i not t
end

plot(t,v);