staRdom (version 1.0.8)

abs_parms: Calculating slopes and slope ratios of a data frame of absorbance data.

Description

Calculating slopes and slope ratios of a data frame of absorbance data.

Usage

abs_parms(abs_data, cuvle, limits = list(c(275, 295), c(350, 400), c(300,
  700)), l_ref = list(350, 350, 350), S = TRUE, lref = FALSE, p = FALSE,
  model = FALSE, cores = parallel::detectCores()/2)

Arguments

abs_data

data frame containing absorbance data.

cuvle

length of used cuvette in cm

limits

list with vectors containig upper and lower bounds of wavelengeth ranges to be fitted

l_ref

list with reference wavelengths, same length as limits

S

logical, include slope parameter in the table

lref

logical, include reference wavelength in the table

p

logical, include ps of the coefficients in the table

model

logical, include complete model in data frame

cores

number of cores to be used for parallel processing

Value

A data frame containing the adsorption slopes and slope ratios in column, one line for each sample.

Details

The absorbance data is a data frame with the first column called "wavelength" containg the wavelength. Each other column contains the data from one sample. You can use absorbance_read to read in appropriate data.

The following spectral parameters are calculated:

• $S_275-295$ slope between 275 and 295 nm calculated with nonlinear regression

• $S_350-400$ slope between 350 and 400 nm calculated with nonlinear regression

• $S_300-700$ slope between 275 and 295 nm calculated with nonlinear regression

• SR slope ratio, calculated by $S_275-295$/$S_350-400$

• E2:E3 ratio $a_250$/$a_365$

• E4:E6 ratio $a_465$/$a_665$

• $a_254$ absorbance at 254 nm

• $a_300$ absorbance at 300 nm

Depending on available wavelength range, values might be NA. Additionally other wavelength limits can be defined. The slope ratio might fail in this case. For further details please refer to Helm et al. (2008).

References

Helms, J., Kieber, D., Mopper, K. 2008. Absorption spectral slopes and slope ratios as indicators of molecular weight, source, and photobleaching of chromophoric dissolved organic matter. Limnol. Oceanogr., 53(3), 955<U+2013>969 http://onlinelibrary.wiley.com/doi/10.4319/lo.2008.53.3.0955/pdf

Examples

# NOT RUN {
data(abs_data)
abs_parms(abs_data[,1:5],5)
abs_parms(abs_data[,1:5],5,l_ref=list(NA,NA,NA), lref=TRUE) # fit lref as well
# }