Question about function (PLOTING)

Dear fellows,

I have question about some function which I can not plote.

function d = f (a,b,x)

d(x>0 & x<=a) = 9.2.*x.*a./(3.*a+4.*b-x)

d(x>a & x<=b) = 1.2.*a.*b./x;

d(x>b) = 3*x.^2./(a.*b);

Like you see, function is nothing special.

This function works for single values, but as you know to plot some function it is necessary for x to be array.

And I don't know how to solve these conditions x>b, x>a....

How to compare one single value with array, beacuse I need to compare every element of array x with a or b or 0?

Thank you very much dear fellows for any answer.

Answer 1

[Daniel Shub]

Assuming a and b are scalars and x is a vector ...

d = zeros(size(x));
d(x>0 & x<=a) = 9.2.*x(x>0 & x<=a).*a./(3.*a+4.*b-x(x>0 & x<=a));
d(x>a & x<=b) = 1.2.*a.*b./x(x>a & x<=b);
d(x>b) = 3*x(x>b).^2./(a.*b);

Basically, everywhere there is an x, you need to put the condition.