Subscript indices must either be real positive integers or logicals.

Question

nathan Short 2019-9-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480753-subscript-indices-must-either-be-real-positive-integers-or-logicals

评论： nathan Short 2019-9-17

Why do i get " Subscript indices must either be real positive integers or logicals." when i run my code and how can i fix it

%% problem parameters

P = 0.5*9.81; % [load N]

L = 0.5; % [Length M]

E = 69*10^6;

I = ((0.0032^3)*(0.0088))/12;

%%

x = (0:0.025:L);

v = zeros(length(x));

for i = 0.025:length(a)

a = 1/(E*I);

b = 1/12;

c = 1/16;

v(i) = a*((b*P*(i^3))-(1*c*P*(L^2)));

end

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Answer 1

KALYAN ACHARJYA 2019-9-17

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480753-subscript-indices-must-either-be-real-positive-integers-or-logicals#answer_392245

编辑：KALYAN ACHARJYA 2019-9-17

在 MATLAB Online 中打开

The error is

 v(i) 
%..^

In Matlab indexing, the i value must be positive interger, like 1,2,3,,,,

v(1)>> Allow

v(0)>> Not Allow

v(0.25)>> Not Allow

v(-3)>> Not Allow

v(7)>> Allow

Hope you get the sufficients hints. In your case i starts from 0.25, hence v(0.25) Not allowed.

% Define a
% ????
%% problem parameters
P = 0.5*9.81;      % [load N]
L = 0.5;            % [Length M]
E = 69*10^6;
I = ((0.0032^3)*(0.0088))/12;
%%
x = (0:0.025:L);
v = zeros(length(x));
i=0.025:length(a) 
for j =1:length(i) 
    a = 1/(E*I);
    b = 1/12;
    c = 1/16;
v(j)= a*((b*P*(i(j)^3))-(1*c*P*(L^2)));
end

Without Loop:

% Define a
% ????
%% problem parameters
P = 0.5*9.81;      % [load N]
L = 0.5;            % [Length M]
E = 69*10^6;
I = ((0.0032^3)*(0.0088))/12;
%%
x = (0:0.025:L);
v = zeros(length(x));
i=0.025:length(a) 
a=1/(E*I);
b=1/12;
c=1/16;  
v=a*((b*P.*(i.^3))-(1*c*P*(L^2)));