### Syntax

`p = sw_res(source,poldeg)`

`p = sw_res(source,poldeg,true)`

### Description

`p = sw_res(fid,poldeg)`

reads tabulated resolution data from the
`source`

file which contains the FWHM energy resolution values as a
function of energy transfer in two columns. First column is the energy
transfer values (positive is energy loss), while the second is the FWHM
of the Gaussian resolution at the given energy transfer.

`p = sw_res(fid,poldeg,plot)`

the polynomial fit will be shown in a
figure if `plot`

is true.

### Examples

This example shows how to fit a tabulated resolution data (MERLIN energy resolution for \(E_i=50\) meV and 300 Hz chopper frequency). Using the fitted polynomial, the energy resolution can be calculated at an arbitrary energy transfer value.

```
resDat = [0 2.31;10 1.80;20 1.37;30 1.02;40 0.78;49 0.67]
```

*Output*

```
resDat =
0 2.3100
10.0000 1.8000
20.0000 1.3700
30.0000 1.0200
40.0000 0.7800
49.0000 0.6700
```

```
polyRes = sw_res(resDat,3)
```

```
EN = 13
dE = polyval(polyRes,EN)
```

*Output*

```
dE =
1.6635
```

### Input Arguments

`source`

- String, path to the resolution file or a matrix with two columns, where the first column gives the energy transfer value and second column gives the resolution FWHM.
`polDeg`

- Degree of the fitted polynomial, default value is 5.
`plot`

- If
`true`

the resolution will be plotted, default value is`true`

.

### Output Arguments

`p`

- The coefficients for a polynomial \(p(x)\) of degree \(n\) that is a best fit (in a least-squares sense) for the resolution data. The coefficients in \(p\) are in descending powers, and the length of \(p\) is \(n+1\): \[p(x)=p_1\cdot x^n+p_2\cdot x^{n-1}+...+p_n\cdot x+p_{n+1}\]

### See Also

[polyfit] | sw_instrument