You can use dtostrf function to get the float into a string.
http://www.nongnu.org/avr-libc/user-manual/group__avr__stdlib.html#ga060c998e77fb5fc0d3168b3ce8771d42
Then, if the original float is in between 0 and 1, you trim one character from the left, the zero, out. Or trim all character to the left of the decimal separator out.
I'll have to study how do you manipulate strings with Arduino, but how is this for a start?
Edit: Maybe I read that too quickly. I don't understand the input values in your case. If you had the integer and fraction as wholes, you could just combine them into a string, separated with a dot. But if you insist on having the fractional part in a float, the above is something I would look into except the fractional should always be greater or equal to zero and smaller than 1. If I understood the setup correctly.