# Euler's Method using a for loop

조회 수: 6 (최근 30일)
Peter Bohlen 2024년 5월 21일
댓글: Les Beckham 2024년 5월 21일
I am trying to produce a graph of displacement vs. velocity of a falling parachuter and produce tabulated values. I have been given the function--which I have attached a screenshot of. My code is currently producing the error: "Array indices must be positive integers or logical values.
My Code:
clear all
%initial conditions
g0 = 9.81; %m/s^2
R = 6.37e6; %m
h = 10000; %Step Size in m
x = 0 : h : 100000; % Range of X values
v = zeros(size(x));
vi = 1400; %m/s Initial velocity
n = numel(v); % Number of values for velocity
for i=1:n-1
v(x(i+1)) = v(x(i)) + ((g0/v(x(i))) * (R^2/ ((R + x(i))^2))) * (x(i+1) - x(i));
end
plot (x(i),v(i))

댓글을 달려면 로그인하십시오.

### 채택된 답변

Les Beckham 2024년 5월 21일
I'm not sure I believe that the equation given in your attached image is correct. However, the changes below allow the code to run so that you can work out the details.
%initial conditions
g0 = 9.81; %m/s^2
R = 6.37e6; %m
h = 10000; %Step Size in m
x = 0 : h : 100000; % Range of X values
v = zeros(size(x));
v(1) = 1400; %m/s Initial velocity <<<<< initialize the first element of v
n = numel(v); % Number of values for velocity
for i=1:(n-1)
v(i+1) = v(i) + ((g0/v(i)) * (R^2/ ((R + x(i))^2))) * (x(i+1) - x(i));
% ^^-----^^----------^^------index using i rather than x(i)
end
plot (x,v) % << change to plot the entire v vector against the entire x vector
grid on
##### 댓글 수: 2없음 표시없음 숨기기
Peter Bohlen 2024년 5월 21일
Thank you very much for your help!!!
Les Beckham 2024년 5월 21일
You are quite welcome.
Also, if you are just getting started with Matlab, I would highly recommend that you take a couple of hours to go through the free online tutorial: Matlab Onramp

댓글을 달려면 로그인하십시오.

### 카테고리

Help CenterFile Exchange에서 Loops and Conditional Statements에 대해 자세히 알아보기

R2021a

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by