Description Usage Arguments Details Value Author(s) References Examples
The function calculates event and pointer years on a data.frame
with treering series using the normalization in a moving window method introduced by Cropper (1979; cf. Schweingruber et al. 1990). This method ztransforms tree growth in year i
within a symmetric moving window of n
years, thereby providing the number of standard deviations that tree growth deviates in individual years (Cropper values, C) from the window average. To identify event years, one absolute threshold on the number of standard deviations can be set (cf. Cropper 1979), or, alternatively, three intensity classes (cf. Neuwirth et al. 2007). Threshold values for defining event and pointer years can be adjusted.
Prior to the calculation of event and pointer years with pointer.norm
, a 13year weighted lowpass filter, as described by Fritts (1976), may be applied on the treering series using lowpass13
. According to Cropper (1979), such a filter improves the detection of event and pointer years for complacent series, whereas for sensitive series filtering has little effect.
1 2 3  pointer.norm(data, window = 5, method.thresh = c("Cropper", "Neuwirth"),
C.thresh = 0.75, N.thresh1 = 1, N.thresh2 = 1.28,
N.thresh3 = 1.645, series.thresh = 75)

data 
a 
window 
an 
method.thresh 
a 
C.thresh 
a 
N.thresh1 
a 
N.thresh2 
a 
N.thresh3 
a 
series.thresh 
a 
The function ztransforms tree growth in year i
within a symmetric moving window of n
years. For method.thresh
"Cropper"
, event years are defined as those years having absolute Cropper values above a specified threshold (defaults to C > 0.75). For method.thresh
"Neuwirth"
, three classes of distinct growth deviations can be defined, being 'weak', 'strong' and 'extreme' (defaults to C > 1, C > 1.28, and C > 1.645). The window size can be adjusted, as well as the minimum percentage of trees that should display a positive (or negative) event year for that year to be considered as positive (or negative) pointer year.
Note that the resulting time series are truncated by (window1)/2
at both ends inherent to the calculation methods.
The function returns a list
containing the following components:
for method.thresh
"Cropper"
:
Cvalues 
a 
EYvalues 
a 
out 
a 














spec.param 
a 
for method.thresh
"Neuwirth"
:
Cvalues 
a 
EYvalues 
a 
out 
a 






















spec.param 
a 
Marieke van der MaatenTheunissen and Ernst van der Maaten.
Cropper, J.P. (1979) Treering skeleton plotting by computer. TreeRing Bulletin 39: 4759.
Fritts, H.C. (1976) Tree rings and climate. Academic Press Inc. (London) Ltd.
Neuwirth, B., Schweingruber, F.H. and Winiger, M. (2007) Spatial patterns of central European pointer years from 1901 to 1971. Dendrochronologia 24: 7989.
Schweingruber, F.H., Eckstein, D., SerreBachet, F. and Br<c3><a4>ker, O.U. (1990) Identification, presentation and interpretation of event years and pointer years in dendrochronology. Dendrochronologia 8: 938.
1 2 3 4 5 6 7 8 9 10 11 12  ## Calculate pointer years on treering series using method.thresh "Cropper"
## and a userdefined threshold for eventyear definition of 1
data(s033)
py_c < pointer.norm(s033, window = 5, method.thresh = "Cropper",
C.thresh = 1, series.thresh = 75)
py_c$out
## Calculate pointer years on treering series using method.thresh "Neuwirth"
data(s033)
py_n < pointer.norm(s033, window = 5, method.thresh = "Neuwirth",
series.thresh = 75)
py_n$out

Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.