NA Sawthooth signal

Question

How could be possible to represent (plot and numerically) a sawthooth signal in R from:

y <- c(NA,NA,NA,NA,1,NA,NA,NA,1,NA,NA,NA,NA,NA,1,NA,NA,NA,NA,1,NA)

where 1 represents in y the time points when the sawtooth achieves a peak (obviously to 1). Note that the distance between peaks are unequal.

I thought about using interpolation but maybe it is unnecessary.

Thank you,

Answer 1

You can create a sequence of falling numbers like this:

peaks <- c(0, which(!is.na(y)), length(y))

drop <- -1/max(diff(peaks))

df <- do.call(rbind, lapply(diff(peaks), function(x) {
  data.frame(x = c(0, rep(1, x)), 
             y = c(1, seq(1 + drop, by = drop, length.out = x)))
}))

df$x <- cumsum(df$x)

Which gives this result:

plot(df$x, df$y, type = "l")

Or if you want to be fancy...

library(ggplot2)

ggplot(df, aes(x, y)) +
  geom_line(col = "deepskyblue4", size = 1.5) +
  theme_bw()

^{Created on 2020-09-18 by the reprex package (v0.3.0)}