# Ops.spray

##### Arithmetic Ops Group Methods for sprays

Allows arithmetic operators to be used for spray calculations, such as addition, multiplication, division, integer powers, etc. Objects of class spray are interpreted as sparse multivariate polynomials.

- Keywords
- symbolmath

##### Usage

```
# S3 method for spray
Ops(e1, e2 = NULL)
spray_negative(S)
spray_times_spray(S1,S2)
spray_times_scalar(S,x)
spray_plus_spray(S1,S2)
spray_plus_scalar(S,x)
spray_power_scalar(S,n)
spray_eq_spray(S1,S2)
```

##### Arguments

- e1,e2,S,S1,S2
Objects of class spray, here interpreted as sparse multivariate polynomials

- x
Real valued scalar

- n
Non-negative integer

##### Details

The function `Ops.spray()`

passes unary and binary arithmetic
operators (“`+`

”, “`-`

”, “`*`

”,
“`/`

”,“`==`

”, and “`^`

”) to the
appropriate specialist function.

The most interesting operators are “`*`

” and
“`+`

” which execute multivariate polynomial multiplication
and addition respectively.

Testing for equality uses `spray_eq_spray()`

. Note that
`spray_eq_spray(S1,S2)`

is algebraically equivalent to
`is.zero(S1-S2)`

, but faster (`FALSE`

is returned as soon as
a mismatch is found).

##### Value

The functions all return spray objects except “`==`

”, which
returns a logical.

##### Note

Notes here

##### See Also

##### Examples

```
# NOT RUN {
M <- matrix(sample(0:3,21,replace=TRUE),ncol=3)
a <- spray(M,sample(7))
b <- homog(3,4)
# arithmetic operators mostly work as expected:
a + 2*b
a - a*b^2/4
a+b
S1 <- spray(partitions::compositions(4,3))
S2 <- spray(diag(3)) # S2 = x+y+z
stopifnot( (S1+S2)^3 == S1^3 + 3*S1^2*S2 + 3*S1*S2^2 + S2^3 )
# }
```

*Documentation reproduced from package spray, version 1.0-8, License: GPL (>= 2)*