I am writing code for a function but I get an error message

I have to write a function (g) that satisfies several conditions.

I have tried to do this before, but never successfully.

This is what I have so far:

function mayday=g(x)
if x<-pi
    mayday=-1;
elseif (x>=-pi)&&(x<=pi)
    mayday=cos(x);
else mayday=sin(x)+cos(x);
end

When I call the function with individual x's, it works fine, but when define x as a vector

g(-2*pi:pi/4:2*pi)

I get the error message

 Operands to the || and && operators must be convertible to logical scalar values.

Error in g (line 7)
elseif (x>=-pi)&&(x<=pi)

What am i doing wrong?

thanks for the help

Answer 1

[Kye Taylor]

Just replace && with & and double pipes | | with | to operate on nonscalars.

[Walter Roberson]

That will eliminate the error message, but it will not eliminate the problem of trying to apply an "if" statement to a vector expression.

[Kye Taylor]

An if statement can be applied to a vector expression. It is handled by matlab as

if(vector) = if(all(vector))

which may be the desired behavior.. probably not, but that's a different question.

Answer 2

[Walter Roberson]

Please read about logical indexing.

Answer 3

[Peyman]

NOT RELATED TO THE QUESTION: how did you right your question so clear! I used this help and it doesn't work for me!

[Walter Roberson]

I am not certain what you mean but try http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup