# calc_OSLLxTxRatio

##### Calculate Lx/Tx ratio for CW-OSL curves

Calculate Lx/Tx ratios from a given set of CW-OSL curves assuming late light background subtraction.

- Keywords
- datagen

##### Usage

```
calc_OSLLxTxRatio(Lx.data, Tx.data = NULL, signal.integral,
signal.integral.Tx = NULL, background.integral,
background.integral.Tx = NULL,
background.count.distribution = "non-poisson",
use_previousBG = FALSE, sigmab = NULL, sig0 = 0, digits = NULL)
```

##### Arguments

- Lx.data
'>RLum.Data.Curve or data.frame (

**required**): requires a CW-OSL shine down curve (x = time, y = counts)- Tx.data
'>RLum.Data.Curve or data.frame (

*optional*): requires a CW-OSL shine down curve (x = time, y = counts). If no input is given the Tx.data will be treated as`NA`

and no Lx/Tx ratio is calculated.- signal.integral
vector (

**required**): vector with the limits for the signal integral.- signal.integral.Tx
vector (

*optional*): vector with the limits for the signal integral for the Tx curve. If nothing is provided the value from`signal.integral`

is used.- background.integral
vector (

**required**): vector with the bounds for the background integral.- background.integral.Tx
vector (

*optional*): vector with the limits for the background integral for the Tx curve. If nothing is provided the value from`background.integral`

is used.- background.count.distribution
character (

*with default*): sets the count distribution assumed for the error calculation. Possible arguments`poisson`

or`non-poisson`

. See details for further information- use_previousBG
logical (

*with default*): If set to`TRUE`

the background of the Lx-signal is substracted also from the Tx-signal. Please note that in this case separat signal integral limits for the Tx signal are not allowed and will be reset.- sigmab
numeric (

*optional*): option to set a manual value for the overdispersion (for LnTx and TnTx), used for the Lx/Tx error calculation. The value should be provided as absolute squared count values, e.g.`sigmab = c(300,300)`

.**Note:**If only one value is provided this value is taken for both (LnTx and TnTx) signals.- sig0
numeric (

*with default*): allow adding an extra component of error to the final Lx/Tx error value (e.g., instrumental errror, see details).- digits
integer (

*with default*): round numbers to the specified digits. If digits is set to`NULL`

nothing is rounded.

##### Details

The integrity of the chosen values for the signal and background integral is checked by the function; the signal integral limits have to be lower than the background integral limits. If a vector is given as input instead of a data.frame, an artificial data.frame is produced. The error calculation is done according to Galbraith (2002).

**Please note:** In cases where the calculation results in `NaN`

values (for
example due to zero-signal, and therefore a division of 0 by 0), these `NaN`

values are replaced by 0.

**sigmab**

The default value of `sigmab`

is calculated assuming the background is
constant and **would not** applicable when the background varies as,
e.g., as observed for the early light substraction method.

**sig0**

This argument allows to add an extra component of error to the final Lx/Tx error value. The input will be treated as factor that is multiplied with the already calculated LxTx and the result is add up by:

$$se(LxTx) = \sqrt(se(LxTx)^2 + (LxTx * sig0)^2)$$

**background.count.distribution**

This argument allows selecting the distribution assumption that is used for the error calculation. According to Galbraith (2002, 2014) the background counts may be overdispersed (i.e. do not follow a poisson distribution, which is assumed for the photomultiplier counts). In that case (might be the normal case) it has to be accounted for the overdispersion by estimating \(\sigma^2\) (i.e. the overdispersion value). Therefore the relative standard error is calculated as:

`poisson`

$$rse(\mu_{S}) \approx \sqrt(Y_{0} + Y_{1}/k^2)/Y_{0} - Y_{1}/k$$`non-poisson`

$$rse(\mu_{S}) \approx \sqrt(Y_{0} + Y_{1}/k^2 + \sigma^2(1+1/k))/Y_{0} - Y_{1}/k$$

**Please note** that when using the early background subtraction method in
combination with the 'non-poisson' distribution argument, the corresponding Lx/Tx error
may considerably increase due to a high sigmab value.
Please check whether this is valid for your data set and if necessary
consider to provide an own sigmab value using the corresponding argument `sigmab`

.

##### Value

Returns an S4 object of type '>RLum.Results.

Slot `data`

contains a list with the following structure:

**@data**

$LxTx.table (data.frame) .. $ LnLx .. $ LnLx.BG .. $ TnTx .. $ TnTx.BG .. $ Net_LnLx .. $ Net_LnLx.Error .. $ Net_TnTx.Error .. $ LxTx .. $ LxTx.Error $ calc.parameters (list) .. $ sigmab.LnTx .. $ sigmab.TnTx .. $ k

**@info**

$ call (original function call)

##### Note

The results of this function have been cross-checked with the Analyst (vers. 3.24b). Access to the results object via get_RLum.

**Caution:** If you are using early light subtraction (EBG), please either provide your
own `sigmab`

value or use `background.count.distribution = "poisson"`

.

##### Function version

0.7.0 (2018-02-14 13:41:37)

##### How to cite

Kreutzer, S. (2018). calc_OSLLxTxRatio(): Calculate Lx/Tx ratio for CW-OSL curves. Function version 0.7.0. In: Kreutzer, S., Burow, C., Dietze, M., Fuchs, M.C., Schmidt, C., Fischer, M., Friedrich, J. (2018). Luminescence: Comprehensive Luminescence Dating Data Analysis. R package version 0.8.6. https://CRAN.R-project.org/package=Luminescence

##### References

Duller, G., 2016. Analyst v4.31.9 - User Manual. http://www.nutech.dtu.dk/english/-/media/Andre_Universitetsenheder/Nutech/Produkter-og-services/radiation_measurement_instruments/tl_osl_reader/Manuals/Analyst-Manual.ashx?la=da

Galbraith, R.F., 2002. A note on the variance of a background-corrected OSL count. Ancient TL, 20 (2), 49-51.

Galbraith, R.F., 2014. A further note on the variance of a background-corrected OSL count. Ancient TL, 31 (2), 1-3.

##### See Also

'>RLum.Data.Curve, Analyse_SAR.OSLdata, plot_GrowthCurve, analyse_SAR.CWOSL

##### Examples

```
# NOT RUN {
##load data
data(ExampleData.LxTxOSLData, envir = environment())
##calculate Lx/Tx ratio
results <- calc_OSLLxTxRatio(Lx.data, Tx.data, signal.integral = c(1:2),
background.integral = c(85:100))
##get results object
get_RLum(results)
# }
```

*Documentation reproduced from package Luminescence, version 0.8.6, License: GPL-3*