Ben - 1 year ago 60
R Question

# Find 3 consecutive highest values in circular series in R

i have data in the following form (2 examples):

``````p1 <- structure(c(1.38172177074188, 1.18601365390563, 1.25131938561825,
1.07175353794277, 0.887770295772917, 0.806599968169486, 0.843543355495394,
0.889051695167723, 0.764131945540256, 0.699309441111923, 0.945165791967098,
1.31310409471336), .Dim = 12L)

p2 <- structure(c(1.24801075135611, 1.06280347993594, 1.21410288703334,
1.36797720634294, 1.07291218307332, 0.936924063490867, 0.819723966406961,
0.854960740335283, 0.718565087630857, 0.649827141012991, 0.785853771875901,
1.04368795443605), .Dim = 12L)
``````

These are standardized monthly means of hydrological time series; so-called PardÃ© regimes that give some indication about annual seasonality. To do further analysis, i need to derive the 3 highest and lowest months from these PardÃ© series. Because seasonality can be bimodal, i need to identify the 3 highest/lowest consecutive data points (which are most often not the three absolute highest/lowest data points, see examples) to derive the timing of the most wet and dry periods. Up to now i failed because of the circular character of the time series, which poses a special challenge.
Any suggestions?

You could use `filter`. It sums consecutive values and can deal with circular time series.
``````f1 <- stats::filter(p1, c(1, 1, 1), circular = TRUE, sides = 1)