fixpt_interp1 (Fixed-Point Blockset)

Implement a 1-D lookup table

Syntax

y = fixpt_interp1(xdata,ydata,x,xdt,xscale,ydt,yscale,rndmeth)

Description

fixpt_interp1 implements a lookup table to find output(s) y for input(s) x. If x falls between two xdata values, then y is found by interpolating between the corresponding ydata pair. If x falls above the range given by xdata, y is given as the maximum ydata value. If x falls below the range given by xdata, y is given as the minimum ydata value.

If either the input data type, xdt, or the output data type, ydt, is floating point, then floating-point calculation is used to perform the interpolation. Otherwise, integer-only calculation is used. This calculation handles the input scaling, xscale, and the output scaling, yscale, appropriately, and obeys the designated rounding method, rndmeth.

Example

Define xdata as a vector of 33 evenly spaced points between 0 and 8, and ydata as the sinc of xdata.

xdata = linspace(0,8,33).';
ydata = sinc(xdata);

Now define your input x as a vector of 201 evenly spaced points between -1 and 9.

```
x = linspace(-1,9,201).';
```

Notice that x includes some values that are both lower and higher than the range of xdata.

You can now use fixpt_interp1 to interpolate outputs for x.

y = fixpt_interp1(xdata,ydata,x,sfix(8),2^-3,sfix(16),2^-14,... 
'Floor')

fixpt_convert_prep fixpt_look1_func_approx