Array Indices Must Be Positive Values

Hello, I am trying to compute a value, v_y0. This value uses negative variables and should return a negative value. I don't understand how to assign the variables so I don't get the "array indices must be a positive integer" error. Total beginner here.

% given values
mu = 62750.28;  % nm
R_e = 3443.15;  % miles
h_a = 317;  % nm
h_p = 317;  % nm
t_t = 4320;  % seconds
x_0 = 0;  % feet
y_0 = -48608.924;  % feet

% calculate semimajor axis (nm)
a = (h_a + h_p + 2*R_e)/2;

% calculate mean angular motion (rad/sec)
n = sqrt(mu/(a^3));

% calculate s & c
s = sin(n*t_t);
c = cos(n*t_t);

% calculate velocity in y direction
v_y0 = @(y_0)((6*x_0(n*t_t)-s)-y_0)*n*s-2*n*x_0(4-3*c)*(1-c)/(4*s-3*n*t_t)*s+4*((1-c)^2);

Answer 1

[Star Strider]

The problem is:

v_y0 = @(y_0)((6*x_0(n*t_t)-s)-y_0)*n*s-2*n*x_0(4-3*c)*(1-c)/(4*s-3*n*t_t)*s+4*((1-c)^2);
                   ↑ ← HERE                   ↑ ← HERE

Since ‘x_0’ is a scalar, in the absence of a multiplication (or other) operator, that is considered to be a subscript reference. (Even if it had a legitimate positive integer value, any value greater than 1 would throw an error.) Supply the appropriate operator and the problem should resolve. Note that it may be necessary to use element-wise multiplication (.*) and division (./) for your code to run without error.

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