pvldcurve (version 1.2.6)

FittedFW: Correct continuous fresh weight measurements

Description

Corrects fresh weight, measured continuously on a desiccating leaf for determination of minimum conductance, by fitting the fresh weight values to a combined exponential and linear model

Usage

FittedFW(data, sample = "sample", fresh.weight = "fresh.weight",
  time.since.start = "time.since.start", graph = TRUE,
  show.legend = TRUE)

Arguments

data

data frame, at least with a column containing numeric fresh weight (g) and time since start (min) values, ordered by sample by descending fresh.weight. A column containing the sample IDs is optionally required if several samples were measured.

sample

optional name of the column in data containing the sample IDs, default: "sample"

fresh.weight

optional name of the column in data containing the fresh weight values (g), default: "fresh weight"

time.since.start

optional name of the column in data containing the time since start (min) values, default: "time.since.start"

graph

set FALSE if no plots are to be returned

show.legend

set FALSE if no legend is to be be shown in the plots

Value

the original data frame (data) extended by a numeric column containing the fitted fresh weight values ("fitted.fw")

Details

Determination of minimum conductance via a leaf drying curve requires fresh weight to be measured continuously on a desiccating leaf. The fresh weight values are then used to calculate leaf conductance. If several leaves are measured on one scale, the measurements are prone to noises, which influence conductance values largely. Here, the fresh weight data is corrected for noises by fitting it to a combined linear and exponential model using the port algorithm of nls(). Before using this function, check the raw data for an initial plateau. If the exponential decline does not onset directly, fitting might not succeed.

Examples

# NOT RUN {
# get example data
df <- TimeSinceStart(leaf_drying_data)
# remove plateauing data
df <- df[df$fw.plateau != "yes",]
# extend the data frame by saturated fresh weight
df <- FittedFW(df)

# }