How do i resolve the error in this code:

% Programme for estimating k in DE

prompt= 'input a value for k : ' ;

k = input(prompt);

w =(pi/12);

n=1:100;
k(n+1)=-1*(log(((12*(((k(n))^2)+(w^2))-(5*k(n))*(k(n)*cos(6*w))+(wsin(6*w)))/(17*((k(n)^2)+(w^2))-5*k(n)*(k(n)*cos(5*w))+(w*sin5w)));

disp (k)

the problem seems to be with the semicolon after the log funtion

[Walter Roberson]

You have not indicated what the error is.

Is the user entering a vector or a scalar?

Is k(n) intended to indicate k indexed at n, or k multiplied by n?

Hint: .^ .* ./

[reuben crockett]

a scalar and k indexed at n the error just says missing parenthases

Answer 1

[Star Strider]

The problem is most likely that you are missing several operators (probably multiplication operators), as well as vectorising it here:

k(n+1)=-1*(log(((12*(((k(n))^2)+(w^2))-(5*k(n))*(k(n)*cos(6*w))+(wsin(6*w)))/(17*((k(n)^2)+(w^2))-5*k(n)*(k(n)*cos(5*w))+(w*sin5w)));

See if substituting this helps:

k(n+1)=-1*(log(((12*(((k(n))^2)+(w.^2))-(5*k(n))*(k(n)*cos(6*w))+(w.*sin(6*w)))./(17*((k(n)^2)+(w.^2))-5*k(n)*(k(n)*cos(5*w))+(w.*sin(5*w))));

The parentheses don’t match, so you will need to fix that before you run this line. (I don’t know what you’re doing, so I can’t fix them for you.)

[reuben crockett]

cheers im basically trying to re write an equation into matlab the one found at the top of page 66 of this document

http://www.staff.science.uu.nl/~wepst101/NWI/Wisweek38.pdf

[Star Strider]

It’s easiest to break the statement out into its constituent parts. That makes it easier to read, and easier to troubleshoot:

N = 12*(k(n)^2 + w.^2) - 5*k(n)*(k(n)*cos(6*w) + w.*sin(6*w));
D = 17*(k(n)^2 + w.^2) - 5*k(n)*(k(n)*cos(5*w) + w.*sin(5*w));
k(n+1) = -log(N./D);

The computer has to do all these calculations and command parsing anyway, so you’re not losing any efficiency by creating the separate variables.

You also need to understand the vectorisation I used in those statements. See the documentation on Array vs. Matrix Operations for all the interesting details.

I ran a version of it to be sure it works. (It does.) I leave the rest to you.