Switch/case command function

I'm trying to create a function with the switch /case commands and run it from another program satisfying certain criteria. The files are in the same folder but I'm not sure how to lay out the function and call it for that matter. Here is my function file:

function input = g(x) switch input case x < -pi disp('-1') case g >= -1 && g<= pi cos(g) case g > pi disp('-1')

end

Thanks for you help

Answer 1

[James]

Here is the function that does it (hopefully it is what you want)

function y=g(x)  
if x < -pi 
    y=-1;

elseif (x >= -pi && x<=pi)
    y=cos(x);
elseif x > pi
    y=-1;
end

[Angel Martinez]

Thank you. That makes sense.

[James]

No problem. It seems that you are asking two questions. For the layout of the function and calling from another program:

You can create the function by going to matlab,

1.File -> New-> function

2.Delete everything and paste the code in the code above.

3.Save it at the same folder as your calling program.

4.To use this g function from the main program, just type y=g(x) e.g. g(pi) at your main program function whenever you need to compute g(x).

Answer 2

[James]

Hi Angel,

I'm not sure if I fully understand your problem. However, just a quick glance on it, the case statement is not possible for inequality. I guess you have to use a list of if-elseif :)

Extracted from http://www.mathworks.com/help/techdoc/ref/switch.html: A case_expression cannot include relational operators such as < or > to compare against the switch_expression. To test for inequality, use if-elseif statements.

[Angel Martinez]

Sorry about the vagueness. The problem is from Logical functions and selection structures. And the problem states:

Create a function called g that satisfies the following criteria:

%For x < -pi; g(x)=-1

%For x >= -pi and x<=pi; g(x)=cos(x)

%For x > pi; g(x)=-1

Plot your results for values of x from -2pi to +2pi.

The plotting portion should be fairly easy but I guess I'm just confused with the creating the function since you call the function from the program and that's what i'm not sure hot to setup. sorry so long winded.