Convert number to nearest value representable by specified fixed-point data type
outValue = num2fixpt(OrigValue, FixPtDataType, FixPtScaling,
RndMeth, DoSatur)
num2fixpt(OrigValue, FixPtDataType, FixPtScaling,
RndMeth, DoSatur) returns the result of converting OrigValue to
the nearest value representable by the fixed-point data type FixPtDataType.
Both OrigValue and outValue are
of data type double. As illustrated in the example
that follows, you can use num2fixpt to investigate
quantization error that might result from converting a number to a
fixed-point data type. The arguments of num2fixpt include:
| Value to be converted to a fixed-point representation.
Must be specified using a |
| The fixed-point data type used to convert |
| Scaling of the output in either Slope or [Slope Bias]
format. If |
| Rounding technique used if the fixed-point data type
lacks the precision to represent |
| Indicates whether the output should be saturated to the
minimum or maximum representable value upon underflow or overflow.
If |
Suppose you wish to investigate the quantization effect associated with representing the real-world value 9.875 as a signed, 8-bit fixed-point number. The command
num2fixpt(9.875, sfix(8), 2^-1) ans = 9.50000000000000
reveals that a slope of 2^-1 results in a
quantization error of 0.375. The command
num2fixpt(9.875, sfix(8), 2^-2) ans = 9.75000000000000
demonstrates that a slope of 2^-2 reduces
the quantization error to 0.125. But a slope of 2^-3,
as used in the command
num2fixpt(9.875, sfix(8), 2^-3) ans = 9.87500000000000
eliminates the quantization error entirely.