# sub

Subtract two `fi` objects using `fimath` object

## Syntax

``c = sub(F,a,b)``

## Description

example

````c = sub(F,a,b)` subtracts `fi` objects `a` and `b` using `fimath` object `F`. This is helpful in cases when you want to override the `fimath` objects of `a` and `b`, or if the `fimath` properties associated with `a` and `b` are different. The output of `fi` object `c` has no local `fimath`.```

## Examples

collapse all

```a = fi(pi); b = fi(exp(1)); F = fimath('SumMode','SpecifyPrecision',... 'SumWordLength',32,'SumFractionLength',16); c = sub(F,a,b)```
```c = 0.4233 DataTypeMode: Fixed-point: binary point scaling Signedness: Signed WordLength: 32 FractionLength: 16 ```

`c` is the 32-bit difference of `a` and `b`, with fraction length 16.

## Input Arguments

collapse all

`fimath` object to use for subtraction, specified as a `fimath` object.

Operands, specified as scalars, vectors, matrices, or multidimensional arrays.

`a` and `b` must both be `fi` objects and must have the same dimensions unless one is a scalar. If either `a` or `b` is scalar, then `c` has the dimensions of the nonscalar object.

Data Types: `fi`
Complex Number Support: Yes

## Algorithms

`C = sub(F,A,B)`
or
`C = F.sub(A,B)`

is equivalent to

```A.fimath = F; B.fimath = F; C = A - B;```
except that the `fimath` properties of `A` and `B` are not modified when you use the functional form.

## Version History

Introduced before R2006a