R: Find layers of interest (e.g. PWLs) in snowprofile(Layers)

findPWL {sarp.snowprofile}

R Documentation

Find layers of interest (e.g. PWLs) in snowprofile(Layers)

Description

Find one or more layers of interest, such as persistent weak layers (PWL) in a snowprofile or snowprofileLayers object based on combinations of grain type, datetag, grain size, and stability indices (TSA/ RTA/ critical crack length/ p_unstable) of the layer. The routine can also be used for searching for crusts (or any other grain types).

Usage

findPWL(
  x,
  pwl_gtype = c("SH", "DH"),
  pwl_date = NA,
  date_range = c(-5, 0),
  date_range_earlier = as.difftime(date_range[1], units = "days"),
  date_range_later = as.difftime(date_range[2], units = "days"),
  bdate_range = c(-1, 1),
  bdate_range_earlier = as.difftime(bdate_range[1], units = "days"),
  bdate_range_later = as.difftime(bdate_range[2], units = "days"),
  threshold_gtype = pwl_gtype,
  threshold_gsize = NA,
  threshold_TSA = NA,
  threshold_RTA = NA,
  threshold_SK38 = NA,
  threshold_RC = NA,
  threshold_PU = NA
)

labelPWL(x, ...)

Arguments

`x`	snowprofile or snowprofileLayers object
`pwl_gtype`	a vector of grain types of interest
`pwl_date`	a date of interest given as character ('YYYY-MM-DD') or as POSIXct; set to `NA` to ignore dates. If given as POSIXct, time comparison between layer dates and pwl_date will consider the times of day (i.e., hours, etc). Otherwise only consider year/month/days.
`date_range`	a numeric array of length 2 that defines a date search window around `pwl_date`. This date range is applied to `ddate`s (deposition dates), or if these are not available to `datetag`s.
`date_range_earlier`	a difftime object of `date_range[1]` (must be negative).
`date_range_later`	a difftime object of `date_range[2]` (must be positive).
`bdate_range`	a numeric array of length 2 that defines a date search window around `pwl_date`. This date range is applied to `bdate`s (burial dates)
`bdate_range_earlier`	a difftime object of `bdate_range[1]` (must be negative).
`bdate_range_later`	a difftime object of `bdate_range[2]` (must be positive).
`threshold_gtype`	specific grain types that are only deemed a PWL if they pass one or multiple thresholds (see next parameters)
`threshold_gsize`	a threshold grain size in order to deem `threshold_gtype` a PWL; set to `NA` to ignore grain sizes.
`threshold_TSA`	a threshold TSA value (see computeTSA) in order to deem `threshold_gtype` a PWL; set to `NA` to ignore TSA.
`threshold_RTA`	a threshold RTA value (see computeRTA) in order to deem `threshold_gtype` a PWL; set to `NA` to ignore RTA.
`threshold_SK38`	a threshold SK38 in order to deem `threshold_gtype` a PWL; set to `NA` to ignore this threshold.
`threshold_RC`	a threshold critical crack length in order to deem `threshold_gtype` a PWL; set to `NA` to ignore this threshold.
`threshold_PU`	a threshold value for p_unstable in order to deem `threshold_gtype` a PWL; set to `NA` to ignore this threshold.
`...`	passed on to findPWL

Details

In case date considerations are included in your search, either one of the date window conditions needs to be satisfied to return a given layer:

ddate or datetag within date_range, or
bdate within bdate_range

If the input object contains deposition dates (ddate, mostly in simulated profiles), but no bdates, they are automatically computed by deriveDatetag; otherwise the date window is applied to the datetag (mostly for manual profiles).

If you apply thresholds to your search, only layers are returned that satisfy at least one of the provided thresholds.

The labelPWL wrapper function is primarily used by sarp.snowprofile.alignment::averageSP.

Value

findPWL: An index vector of PWLs that match the desired requirements

labelPWL: The input object with an extra boolean column appended to the layer object, called ⁠$layerOfInterest⁠.

Functions

findPWL(): Find layers of interest (e.g., PWLs) in snowprofile or snowprofileLayers
labelPWL(): Label layers of interest (e.g., weak layers) in snowprofile

Author(s)

fherla

Examples

## get index vector:
findPWL(SPpairs$A_modeled)

## get layers subset:
SPpairs$A_manual$layers[findPWL(SPpairs$A_manual), ]
SPpairs$A_manual$layers[findPWL(SPpairs$A_manual, threshold_gsize = 2.2,
                        threshold_gtype = c("FC", "FCxr")), ]
## all (SH, DH), and (FC, FCxr) >= 1 mm grain size:
SPpairs$A_modeled$layers[findPWL(SPpairs$A_modeled, pwl_gtype = c("SH", "DH", "FC", "FCxr"),
                                 threshold_gsize = 1, threshold_gtype = c("FC", "FCxr")), ]
## use TSA threshold:
SPpairs$A_modeled <- computeTSA(SPpairs$A_modeled)
SPpairs$A_modeled$layers[findPWL(SPpairs$A_modeled, pwl_gtype = c("SH", "DH", "FC", "FCxr"),
                                 threshold_TSA = 4, threshold_gtype = c("FC", "FCxr")), ]

## searching for a specific pwl_date:
## let's construct one layer and an array of pwl_dates
tl <- snowprofileLayers(height = 1, gtype = "SH",
                        ddate = as.POSIXct("2020-12-15"),
                        bdate = as.POSIXct("2020-12-20"))
pwl_dates <- paste0("2020-12-", seq(14, 22))
## which pwl_date will 'find' that layer?
sapply(pwl_dates, function(dt) length(findPWL(tl, pwl_date = dt)) > 0)
## same example, but with bdate being NA:
tl <- snowprofileLayers(height = 1, gtype = "SH",
                        ddate = as.POSIXct("2020-12-15"),
                        bdate = as.POSIXct(NA), dropNAs = FALSE)
sapply(pwl_dates, function(dt) length(findPWL(tl, pwl_date = dt)) > 0)

## pwl_date example with proper profile:
sp <- deriveDatetag(SPpairs$A_manual)
sp$layers
pwl_dates <- paste0("2019-02-", seq(18, 26))
names(pwl_dates) <- pwl_dates
## which pwl_date will 'find' the two layers with (b)date labels?
list(pwl_date = lapply(pwl_dates, function(dt) {
  sp$layers[findPWL(sp, pwl_gtype = c("SH", "FC"), pwl_date = dt),
            c("height", "gtype", "ddate", "bdate")]
}))

## same example as above, but including TSA threshold:
sp <- computeTSA(sp)
## the SH layer has TSA 5, the FC layer has TSA 4:
list(pwl_date = lapply(pwl_dates, function(dt) {
  sp$layers[findPWL(sp, pwl_gtype = c("SH", "FC"), pwl_date = dt, threshold_TSA = 5),
            c("height", "gtype", "ddate", "bdate")]
}))
## --> no more FC layer in output since its TSA value is below the threshold!

## can also be used to search for crusts:
SPpairs$A_manual$layers[findPWL(SPpairs$A_manual, pwl_gtype = "MFcr"), ]

[Package sarp.snowprofile version 1.3.2 Index]