Creating logical arrays based on condition

I have an output array a[0.5,0.7,0.9], a threshold array b[0.3, 0.8, 0.7], and a lookup values array c[0,1,2]

I want a finalOutput array, f, which contains the corresponding values c if a>b else -1.

I decided to use a logical indexing array using the following code for this:

a(a>b)=1;
a(a<=b)=0;
a=logical(a);
f=c(a);

But f only contains the values of c where a=1. How can I write conditional statements to get f=[0,-1,2] ?

I also want to get the logical a in one line, because the second line of code gives incorrect outputs if I change a to [1.5, 0.7, 0.9] and b to [1.3, 0.8, 0.7].

Appreciate all suggestions.

[Walter Roberson]

a(a>b)=1;
a(a<=b)=0;
a=logical(a);

could be replaced with

a = a > b;

Answer 1

[madhan ravi]

c(a<b)=-1
f=c

[Tooba]

c(a<b)=-1 will only replace the values of a which are less than b. What about the values of a which are greater than b?

[madhan ravi]

c(a>b)=.... your desired value 

Answer 2

[Stephen23]

>> a = [0.5,0.7,0.9];
>> b = [0.3,0.8,0.7];
>> c = [0,1,2];
>> f = c;
>> f(a<=b) = -1
f =
   0  -1   2