Array indicates must be positive integers or logical values

%question 3
clf
t= 0:0.01:2;
y3= 8*sin(20*pi*t)+8*sin(22*pi*t);
plot(t,y3)
xlabel('t')
ylabel('y3')


%question 4

clf
t= 0:0.01:2;
expA= exp(-1.2*t);
y4= y3.*expA
plot(t,y4)
xlabel('t')
ylabel('y4')

%question 5
clf
H= [34 -56 23];
J=[9 12 26];
squrH = H.^2;
MagH = sqrt(sum(squrH))
squrJ = J.^2;
MagJ= sqrt(sum(squrJ))
Angle =acos(sum(H.*J) / (sqrt(sum(H.^2)) * sqrt(sum(J.^2))))
angeldeg = Angle*180/pi

[Adam Danz]

The code you provided does not produce the error in the title.

Answer 1

[Image Analyst]

See the FAQ Subscript_indices_must_either_be_real_positive_integers_or_logicals

Answer 2

[Star Strider]

Taking a wild guess, you likely have a variable named plot or sum (or something similar) that is overshadowing a MATLAB function with the same name.

Without the complete error message (all the red text copied from your Command Window and pasted to a Comment here), it is not possible to determine what that overshadowed function is.

Assuming it is sum, the way to determine that is to type this in a script or your Command Window:

which sum -all

If the first line returned is:

sum is a variable.  

you have found the problem.

The solution is to rename the variable to something that makes sense in the context of your code.

Answer 3

[Sridhar SG]

Your code got successfully executed

MATLAB allows storing of any type of value inside the arrays, only the index values of array cannot be fractional numbers, negative integers, zero or complex/imaginary numbers