Array indices must be positive integers or logical values.

y=input('thecomplexvalue of z=');
x=input('therealvalue of z=');
tol=input('the value tolerance tol=');
z=x+1i*y;
funcnew01=z^5+z^3-pi;
funcnew02=diff(funcnew01);
k=0;
if real(z)==0
y=z;
disp('y     funcnew01(y)    funcnew02(y)     k')
disp('........................................')    
while abs(funcnew01(y))>tol
    y=y-(funcnew01(y)/funcnew02(y));
    k=k+1;
end
else
x=z;
disp('x     funcnew01(x)    funcnew(x)     k')
disp('......................................')
while abs(funcnew01(x))>tol
        x=x-(funcnew01(x)/funcnew02(x));
        k=k+1;
end 
end

I get this error in line 20, I'm not shure why I'm trying to make a code for finding the roots of the complex function with the Newton-Raphson method

Answer 1

[the cyclist]

It seems that you have tried to use this line of code:

funcnew01=z^5+z^3-pi;

to define a general function on z. Then you try to use that "function", e.g. like this:

funcnew01(y)

But that is not what that line of code does. Rather that first line of code, simply defines another variable with the value

z^5+z^3-pi

for whatever the value of z is at the time it is executed.

The specific error you are getting is that your code

funcnew01(x)

is trying to index into a variable (which can only be done with positive integers or logicals).

If you want to define a function, you instead need

funcnew01 = @(z) z^5+z^3-pi;

which can then be called and evaluated the way I believe you intend. See the documentation on anonymous functions for details.

You similarly need to fix funcnew02. I'm not sure what you intend there. A derivative?