# a problem with a function

4 views (last 30 days)
Rica on 23 Jul 2013
hi all ! i wrote this simple function
%
function [ output_args ] = fract_int16( input_args )
if input_args<0
output_args=round(2^16+input_args*2^15);
else
output_args=round(input_args*2^15);
end
end
when i use it for negative number for exemple
%
fract_int16(-0.9133)=35609
fract_int16(0.3481)=11409,
both values ARE TRUE
but when use this function in an array i get a false value
%
A=[-0.9133 0.3481]
fract_int16(A)=[-29927 11407]
this is wrong!!
did i make i mistake in writing this function?
thank you all

David Sanchez on 23 Jul 2013
Try this out:
input_args = [-0.9133 0.3481];
output_args = zeros(size(input_args));
for k=1:length(input_args)
if input_args(k)<0
output_args(k)=round(2^16+input_args(k)*2^15);
else
output_args(k)=round(input_args(k)*2^15);
end
end

Narges M on 23 Jul 2013
Edited: Narges M on 23 Jul 2013
Yes, your function is designed to work with one value, and see if that's less than zero or not. So if you want to use it for arrays you need to use a loop either in the function or when calling it. Right now, if any of the array values are less than zero, if would fire TRUE, and then the output would be calculated for the whole array.

Jan on 23 Jul 2013
And a faster vectorized version:
function output_args = fract_int16(input_args)
output_args= 2^16 * (input_args < 0) + round(input_args * 2^15);
end