Mathematical and arithmetic operations on param's, scan's and pvol's

```
# S3 method for scan
Math(x, ...)
# S3 method for pvol
Math(x, ...)
# S3 method for param
Ops(e1, e2)
# S3 method for scan
Ops(e1, e2)
# S3 method for pvol
Ops(e1, e2)
```

- x
object of class

`scan`

, or`pvol`

- ...
objects passed on to the Math functions

- e1
object of class

`param`

,`scan`

,`pvol`

or a number- e2
object of class

`param`

,`scan`

,`pvol`

or a number

an object of the input class

Use caution when applying these manipulations, as there are no consistency checks if the operations lead to interpretable outcomes. For example, when averaging scans with logarithmic values (e.g. DBZ), it might be required to first exponentiate the data before summing.

Attributes are taken from the first object in the operation.

When a `pvol`

is multiplied by a list, in which case arguments are taken from the list per scan.
this requires the list to have the same length as the number of scans.

```
# Locate and read the polar volume example file
scan1 <- example_scan
#add a value of 1 to all scan parameters:
scan2 <- example_scan + 1
# average the scan parameters of two scans:
# NB: requires identical scan parameter names and order!
(scan1 + scan2)/2
#> Polar scan (class scan)
#>
#> parameters: DBZH VRADH RHOHV ZDR PHIDP
#> elevation angle: 0.5 deg
#> dims: 480 bins x 360 rays
```