Error ''Array indices must be positive integers or logical values.'' when putting interval of 0.01 in a for loop

I get an error ''Array indices must be positive integers or logical values.' when i'm trying to execture a for loop with an interval of 0.01, however when the interval is 1, everything is fine. The problem may stem from it not allowing negative numbers in the array.

y = [];
x = [];

for i = 0:0.1:2
    x(i+1) = i
    y(i+1) = i*i + 3*i - 4
end

x = 0

y = -4

Array indices must be positive integers or logical values.

plot(x,y)

This is the entire code, nothing more

Answer 1

[Dyuman Joshi]

The problem stems from the use of 0 and non-integer values as indices.

As the error message states - Arrays indices in MATLAB must be positive integers (or logical values).

You can vectorize your code -

i = 0:0.1:2;
x = i;
y = i.*i + 3*i - 4;

plot(x,y)

Answer 2

[Vignesh]

Hi Rinalds,

You are encountering this error because you are giving a decimal as index of an array in the for loop. You may try changing the following line according to the number of times you want to iterate the loop.

for i = 0:0.1:2

Answer 3

[Alan Stevens]

More like this:

k = 0:0.1:2;
n = numel(k);
for i = 1:n
    x(i) = k(i);
    y(i) = k(i)*k(i) + 3*k(i) - 4;
end

plot(x,y)