"Error: Invalid expression." error when function is called.

function y = I_Zr(angleZ, Z, w, t)
a = 1;
y = Z;
syms n;
while a < length(Z)
    y(a) = 20 + symsum(((50/(pi*n))*cos(n*w*t + angleZ(a)))/Z(a), n, [1, inf]);
    a=a+1;
end
end

I wrote the above code to try to calculate the current through an RCL circuit I have. I have already calculated the Impedence of the circuit with other functions but this one doesn't run for some reason. I think it might be because I am using symsum incorrectly, or don't understand the equation to some degree. Any help is appreciated.

angleZ and Z are both 1x100 doubles, but when I try to run it through the command window, I get the "Error: Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters." error.

[Walter Roberson]

What input are you using for w and t?

Is there a reason you are not including angleZ(end) and Z(end) in your calculation ? Is there a reason you are not using a for loop ?

Which line is the error occuring on?

I used rand() to create angleZ and Z and called

y = I_Zr(angleZ, Z, 2, 5);

without difficulty.

[James Agerton]

I have forgotten what I knew about this program, could you explain what (end) is?

And there's not a reason to not use a for loop other than that I recognised the syntax for while easier than the for syntax.

I'm trying desperately to both remember how to use Matlab and the equations for RLC circuits.

[Walter Roberson]

Z(end) is the last Z. With Z being 1 x 100, it would be Z(100) .

Your code is looping until a < length(Z) and when true it accesses AngleZ(a) and Z(a) . a = 99 works because 99 < 100 so AngleZ(99) and Z(99) would be accessed, but then you increment from 99 to 100, and 100 < 100 is false so you do not access AngleZ(100) or Z(100) and you do not store into y(100) . However you initialized y = Z; so y(100) will be left untouched as Z(100) which might or might not be what you want

for a = 1 : length(Z)
        y(a) = 20 + symsum(((50/(pi*n))*cos(n*w*t + angleZ(a)))/Z(a), n, [1, inf]);
end