Why do I get "Array indices must be positive integers or logical values" when I am trying to plot my functions?

Question

Jenni 2024-1-31

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2076741-why-do-i-get-array-indices-must-be-positive-integers-or-logical-values-when-i-am-trying-to-plot-my

编辑： Austin M. Weber 2024-1-31

采纳的回答： Mathieu NOE

figure(1)

alpha=0.89;

beta=0.89;

gamma=0.5;

c(0)=1;

i(0)=1;

y(0)=2;

for t=1:50

y(t) = c(t) + i(t);

c(t) = alpha*y(t - 1);

i(t) = beta*(c(t) - c(t - 1)) + gamma;

end

plot(y,'LineWidth',2)

hold on

plot(c,'LineWidth',2)

plot(i,'LineWidth',2)

xlabel('Time period')

ylabel('BKT (M€)')

Hey! I am trying to plot this, but for some reason I get the message "Array indices must be positive integers or logical values". What seems to be the problem in my code?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Mathieu NOE 2024-1-31

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2076741-why-do-i-get-array-indices-must-be-positive-integers-or-logical-values-when-i-am-trying-to-plot-my#answer_1400616

在 MATLAB Online 中打开

hello

1/ matlab is a language where indexing is 1 based and not zero based

2/ next correction is that y must be computed once c and i are updated in the for loop

so a working code is :

figure(1)
alpha=0.89;
beta=0.89;
gamma=0.5;
c(1)=1;
i(1)=1;
y(1)=2;
for t=2:50
    c(t) = alpha*y(t - 1);
    i(t) = beta*(c(t) - c(t - 1)) + gamma;
    y(t) = c(t) + i(t);
end
plot(y,'LineWidth',2)
hold on
plot(c,'LineWidth',2)
plot(i,'LineWidth',2)
xlabel('Time period')
ylabel('BKT (M€)')

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Jenni 2024-1-31

Excellent! Thank you for your help!

请先登录，再进行评论。

Answer 2

Austin M. Weber 2024-1-31

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2076741-why-do-i-get-array-indices-must-be-positive-integers-or-logical-values-when-i-am-trying-to-plot-my#answer_1400646

编辑：Austin M. Weber 2024-1-31

在 MATLAB Online 中打开

In MATLAB, indexing starts at 1, so you cannot have C(0), i(0), or y(0). Rather, it needs to be C(1), i(1), or y(1).

EDIT: @Mathieu NOE is correct, in addition to what I said, that also means that you need to start your for-loop at index position 2 instead of position 1. Otherwise, when your script gets to this line: