arf class public methods

```
  arf()
```
```
  arf(const arf& a)
```
```
  arf(const string filename, const Integer ARFnumber = 1,
      const Integer RowNumber = 1)
```
Constructors. The first is the default constructor, the other two are constructor versions of the copy and read methods described below.
```
   ~arf()
```
Default destructor.
```
   Integer read(string filename, Integer ARFnumber = 1,
                Integer RowNumber = 1)
```
Read file into an object. If ARFnumber is given read from the SPECRESP extension with EXTVER=ARFnumber. The third option is to read an arf from the RowNumber row of a type II file.

  arf& copy(const arf&)

  arf& operator= (const arf&)

Deep copy.

```
  string disp() const
```
Display information about the arf. - return as a string.
```
  void clear()
```
Clear information from the arf.
```
  string check() const
```
Check completeness and consistency of information in the arf, if there is a problem then return diagnostic in string.
```
 rebin(grouping&)
```
Rebin the arf using the input grouping.
```
 Integer write(const string filename, const string sourceFilename="")
```
Write arf as type I file. Note that if the output filename exists and already has a SPECRESP extension then this method will write an additional SPECRESP extension provided that no sourceFilename is given. If sourceFilename is given then the primary HDU and any other extra HDUs are copied into the output file as well as any extra keywords or columns in the spectrum extension.
```
  arf& operator*=(const Real&)
```
Multiply by a constant.
```
  arf& operator+=(const arf&)
```
Add another arf.

  Integer checkCompatibility(const arf&) const

Check compatibility with another arf.

```
 Integer convertUnits()
```
Convert the energies on which the arf is calculated from the current units to keV. The allowed units are keV, MeV, GeV, Hz, angstrom, cm, micron, nm.

  Integer NumberEnergyBins() const

  Integer getNumberEnergyBins() const

Return size of RealVectors.