There are most likely multiple numbers coming in the serial port, and therefore fscanf will return an array of values.
Code:
>> s = '455.54 55.5'
s =
455.54 55.5
>> data(1) = sscanf(s, '%f')
In an assignment A(I) = B, the number of elements in B and I
must be the same.
>> data = sscanf(s, '%f')
data =
455.5400
55.5000
I'm using sscanf on a string rather than fscanf on a serial port, but I would assume the result to be the same