which.floodPeaks: Extracting peaks
In martindurocher/floodStat: FloodNet Regional Frequency Analysis

Description Usage Arguments Details References Examples

Returns the indices of the peaks above a threshold according to the declustering method put in place by the Water Resources Council or simple run declustering. See Lang et al. (1999) for more details.

which.floodPeaks(x, ...)

## S3 method for class 'numeric'
which.floodPeaks(x, dt = NULL, u, r = 1,
  rlow = 0.75, ini = "wrc")

## S3 method for class 'formula'
which.floodPeaks(form, x, u, ...)

## S3 method for class 'data.frame'
which.floodPeaks(x, u, ...)

which.clusters(x, ...)

## S3 method for class 'formula'
which.clusters(form, x, u, r = 1)

## S3 method for class 'numeric'
which.clusters(x, dt = NULL, u, r = 1)

x, form

If numeric, x is a vector of data. If a formula is passed

dt

Date or time of observations. If not provided, regular step are asumed.

@param u Threshold.

r, rlow, ini

Declustering parameters. See details.

Two conditions are required for peaks to not be rejected. First, two peaks Q1 and Q2 must be separated by a period of at least r days, where one recommendation is

4 days + log(A)

and A is the drainage area in squared kilometers. The second conditions is

Xmin > rlow * min(Q1,Q2).

where Xmin is lowest point between Q1 and Q2. By defautlt, rlow = 0.75. When one of the two conditions is not statisfied the lowest of the two peaks is discarded. The 2 conditions are verify sequentially, from an initial set of peaks. If ini = 'run', a run declustering method with one lag is first used to filter the initial set of peaks to the maximums of the respective clusters. If ini = 'lmax' the 2 condition are verified accross all local maximums. If ini = 'wrc' (default), the second condition id verified next the first condition is verify on the previously extracted peaks. The two version are very similar and differ only on few cases where the modified version is more conservative and reject peaks that are kept in the initial version.

The function which.clusters is returning the indices of the peaks identified by the run declustering method where clusters are separated by a period of r consecutive values under the threshold.

Lang M, Ouarda TBMJ, Bobée B. (1999) Towards operational guidelines for over-threshold modeling. Journal of Hydrology. Dec 6;225(3):103–17.

# Declustering using the flood recommendation.
cid <- which.floodPeaks(flow~date, flowStJohn, u = 1000, r = 14, rlow = .75,
                         ini = 'wrc')

plot(flowStJohn, type = 'l')
points(flowStJohn[cid,], col = 'red', pch = 16)

## Simpler run declustering
cid <- which.clusters(flowStJohn$flow, u = 1000, r = 14)

plot(flowStJohn, type = 'l')
points(flowStJohn[cid,], col = 'red', pch = 16)