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When you encounter a function that is not supported for conversion, you can temporarily leave that part of the algorithm in floating point.
The following code returns an error because the log function is not supported for fixed-point inputs.
x = fi(rand(3),1,16,15); y = log(x)
Cast the input, x, to a double, and then cast the output back to a fixed-point data type.
y = fi(log(double(x)),1,16)
y = -0.2050 -0.0906 -1.2783 -0.0990 -0.4583 -0.6035 -2.0637 -2.3275 -0.0435 DataTypeMode: Fixed-point: binary point scaling Signedness: Signed WordLength: 16 FractionLength: 13
This casting allows you to continue with your conversion until you can find a replacement.
You can replace many functions that are not supported for fixed-point conversion with a lookup table. For an example, see Implement Fixed-Point Log2 Using Lookup Table.
You can approximate the results of a function that is not supported for fixed-point with a polynomial approximation. For an example, see Calculate Fixed-Point Arctangent.
You can also write your own function that supports fixed-point inputs. For example, using the mod function, which does support fixed-point inputs, you can write your own version of the rem function, which does not support fixed-point inputs.