[R] Identification of Turning Points in a Signal

[Abby Spurdle]

Sorry no one replied sooner.

Note that I find your question difficult to follow.

It sounds like you have two datasets, each with different sizes.
(e.g. Two data.frame objects, each with a different numbers of rows).

Given that tp$pits is a logical index, trying to apply it to a vector
(or data.frame) of a different size is problematic.
Assuming that you're dealing with datasets of different sizes, the
simplest solution is to modify your code, such that they're the same
size.


On Mon, Feb 10, 2020 at 6:40 PM Ogbos Okike <giftedlife2014 using gmail.com> wrote:
>
> Dear Friends,
> Wishing you the best of the day.
>
> I have a data (Cosmic Ray) which exhibit flow patterns of a
> sine/cosine wave, i.e. decreasing/increasing and registering crests
> (points maximal increases) and troughs/pits (points maximal
> decreases). These turning points are of interest to me. With pastecs
> package and a few lines of code as (the residual is coming from
> Fourier transformation of the data):
> library(pastecs)
>  tp<-turnpoints(data$residual)
>  res<-(1:length(data$residual))[tp$pit]
>  minima<-which(tp$pit & data$residual<= -100)
>  dates<-data$date[minima]
>  k<-data$residual[minima]
> I usually pick all the turning points (trough) equal or below -100. If
> I change the <= to >=, I pick all the crests.
>
> Now, without first transforming the data, I wish to pick the same
> turning points in the raw data. Indeed, the difference between the
> transformed data and the raw data lies only in the amplitude of the
> crest or trough, otherwise, the crests and trough are the same in both
> signals.
>
> When I tried the above code in the raw signal, the warning/error message is:
> Warning message:
> In tp$pit & data$residual <= -100 :
>   longer object length is not a multiple of shorter object length.
>
> A sample of the raw data is:
> 03 10 01 6.20636953199224
> 03 10 02 6.90829266565563
> 03 10 03 6.40434785174345
> 03 10 04 6.33235573547028
> 03 10 05 5.99039318317273
> 03 10 06 5.09049172975812
> 03 10 07 4.35257253795814
> 03 10 08 4.49655677050448
> 03 10 09 4.49655677050448
> 03 10 10 4.4425626832996
> 03 10 11 5.16248384603129
> 03 10 12 5.72042274714835
> 03 10 13 6.26036361919711
> 03 10 14 5.8284109215581
> 03 10 15 5.30646807857763
> 03 10 16 5.32446610764592
> 03 10 17 5.68442668901176
> 03 10 18 6.33235573547028
> 03 10 19 6.80030449124588
> 03 10 20 7.26825324702148
> 03 10 21 6.83630054938246
> 03 10 22 2.53477160206063
> 03 10 23 2.55276963112892
> 03 10 24 2.39078736951429
> 03 10 25 -0.48889728141246
> 03 10 26 -0.110938670978323
> 03 10 27 0.303015997592397
> 03 10 28 1.81485043932894
> 03 10 29 -8.04806949009518
> 03 10 30 -16.1471825708267
> 03 10 31 -17.0470840242413
> 03 11 01 -13.6094604721975
> 03 11 02 -8.98396700164638
> 03 11 03 -6.28426264140255
> 03 11 04 -5.78031782749036
> 03 11 05 -3.72854251370505
> 03 11 06 -2.95462726376849
> 03 11 07 -4.52045579270991
> 03 11 08 -3.54856222302213
> 03 11 09 -0.884853920914888
> 03 11 10 0.447000230138735
> 03 11 11 0.0150475324997218
> 03 11 12 -0.308916990729538
> 03 11 13 0.0690416197045984
> 03 11 14 -0.110938670978323
> 03 11 15 -0.938848008119764
> 03 11 16 -3.02661938004166
> 03 11 17 -3.92652083345627
> 03 11 18 -3.24259572886117
> 03 11 19 -1.67676719991974
> 03 11 20 -2.30669821730997
> 03 11 21 -2.9366292347002
> 03 11 22 -2.75664894401728
> 03 11 23 -3.44057404861238
> 03 11 24 -4.34047550202699
> 03 11 25 -3.87252674625139
> 03 11 26 -2.72065288588069
> 03 11 27 -2.25270413010509
> 03 11 28 -1.37080070575878
> 03 11 29 -0.0389465547051547
> 03 11 30 0.033045561568014
> the first three columns are year, month and day, the last column % CR variation.
>
> abline (h=0) specifies values below the average. I am interested in
> picking the time and magnitude of all the turning points below zero.
>
> Thank you for assisting me.
> Best regards
> Ogbos
>
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