Index exceeds the number of array elements. Index must not exceed 1.

Question

Alina Abdikadyr 2023-2-8

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https://ww2.mathworks.cn/matlabcentral/answers/1908935-index-exceeds-the-number-of-array-elements-index-must-not-exceed-1

评论： Les Beckham 2023-2-8

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Could you please help me to solve the problem. I'm trying to calculate the difference between heights in a loop.

But it gives error "Index exceeds the number of array elements. Index must not exceed 1."

My code is

clear all; close all
W = 10000;
S = 40;
AR = 7;
cd0 = 0.005;
k = 1 / pi / AR;
j=0;
hv=6:-.01:0;
figure(1);hold on; xlabel('h');ylabel('V')
for h1=6:-.01:0
    j=j+1;
    cdminp=4*cd0;
    rho1(j)=1.225*exp(-h1/10.4);
    clminp=sqrt(3*cd0/k);
    Vminp(j)=sqrt(2*W/rho1(j)/S/clminp);
    dh(j)=h1(j)-h1(j+1);
end
figure(1); plot(hv, Vminp);
set(gca, 'XDir','reverse');

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Alina Abdikadyr 2023-2-8

Thank you! I want to calculate the difference between the first element and the folloing elements.

If my h1=6:-.01:0

Probably I should write as:

dh=h1(1)-h1(j+1);

so I need to get the values of dh = 0.01;0.02;0.03;0.04 and so on

Les Beckham 2023-2-8

在 MATLAB Online 中打开

If you know what the h1 vector is already, you don't need a loop to calculate the accumulated difference between elements of it.

h1=6:-.01:0;
dh = -cumsum(diff(h1));
dh(1:10) % look at the first ten elements
ans = 1×10
    0.0100    0.0200    0.0300    0.0400    0.0500    0.0600    0.0700    0.0800    0.0900    0.1000

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Answer 1

Dyuman Joshi 2023-2-8

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1908935-index-exceeds-the-number-of-array-elements-index-must-not-exceed-1#answer_1166740

在 MATLAB Online 中打开

You can do that without the loop

W = 10000;

S = 40;

AR = 7;

cd0 = 0.005;

k = 1 / pi / AR;

hv = 6:-.01:0;

cdminp = 4*cd0;

clminp = sqrt(3*cd0/k);

rho1 = 1.225.*exp(-hv./10.4);

Vminp = (2.*W./rho1./S).^(1/2);

dh = hv(1)-hv(2:end)

dh = 1×600

0.0100 0.0200 0.0300 0.0400 0.0500 0.0600 0.0700 0.0800 0.0900 0.1000 0.1100 0.1200 0.1300 0.1400 0.1500 0.1600 0.1700 0.1800 0.1900 0.2000 0.2100 0.2200 0.2300 0.2400 0.2500 0.2600 0.2700 0.2800 0.2900 0.3000

figure(1);

hold on;

xlabel('h');ylabel('V')

plot(hv,Vminp)

set(gca, 'XDir','reverse');