R - My conditional and nested for loop take too long. How to vectorize? -

i have following code for loop contains conditional if-statement included last 10 loop cycles search change in logical pattern, , increment counter on true:

for(ii in 100:sp)  {      if(start(ii) == 1 && mean(start(ii-11:ii-1)) == 0)      {           count = count + 1      } } 

the value of sp 3,560,400; meaning loop of 3 million plus times. load time enormous, 40 minutes execute loop.

how can optimize code using perhaps vectorization?

thank help.

edit

i have included of code here can see happening:

# store current directory initial.dir<-getwd() # change new directory setwd("h:/r/range") # load necessary libraries - sound library(sound) library(ttr)  ##################################################### # load .wav file / set output file #####################################################  # set output file sink("rangetmp3.out")  # load dataset sndsample <- loadsample('range.wav') fs <- rate(sndsample) nbits <- bits(sndsample)  # assign sound wave y <- sound(sndsample)    ##################################################### # constants #####################################################  #(m/s) speed of light c <- 3e8   ############################ # |- radar parameters ############################  #(s) pulse time tp <- 20e-3  # number of samples per pulse n <- tp*fs  #(hz) lfm start frequency example fstart <- 2260e6  #(hz) lfm stop frequency example fstop <- 2590e6  #(hz) lfm start frequency ism band fstart <- 2402e6  #(hz) lfm stop frequency ism band fstop <- 2495e6  #(hz) transmti bandwidth bw <- fstop-fstart  #instantaneous transmit frequency f <- seq(fstart, fstop, length=n/2)   #range resolution rr <- c/(2*bw) max_range <- rr*n/2  ##################################################### # range #####################################################  ############################ # |- input appears inverted ############################  trig <- -1*y[1,] s <- -1*y[2,]  #reset y #y = 0  ############################ # |- parse data here triggering off rising edge of sync pulse ############################  # reset counter / threshold count <- 0 thresh <- 0  # assign logical vector meets thresh  start <- (trig > thresh)  sp <- nrow(start)-n  for(ii in 100:sp)  {      if(start(ii) == 1 && mean(start(ii-11:ii-1)) == 0)      {           count = count + 1      } } 

edit #2: matlab loop

for ii = 100:(size(start,1)-n)      if start(ii) == 1 && mean(start(ii-11:ii-1)) == 0          count = count + 1;          sif(count,:) = s(ii:ii+n-1);          time(count) = ii*1/fs;      end end 

you can in single line 2 lines, follows:

library(ttr) shiftindx <- c(6:length(start), 1:5) count <- sum(start == 1  &  sma(start, n=11)[shiftindx] == 0, na.rm=true) 

where sma ttr packages

here explanation, piece piece

## give logical vector of t/f ##    length equal length of start start == 1  ## part give smiple moving average of every 11 numbers sma(start, n=11)  ## need shift these on centered properly.  ##   `shiftindx` takes first `floor(11/2)` ma's , puts them @ tail.  ##    (notice these na.) shiftindx <- c(6:length(start), 1:5) sma(start, n=11)[shiftindx]  ## .. checking if equal 0 give t/f vector,  ##     of length equal length of start sma(start, n=11)[shiftindx]  == 0  ## combining t/f vectors using `&` gives t/f vector  ##   of same length, true _both_ of original  ##   vectors true (start == 1)   &   (sma(start, n=11)[shiftindx] == 0)  ## taking `sum(.)` of logical vector equivalent of counting ##    how many true values in vector.  ## snce incrementing `count` every time both conditional statements true,  ##    final value of `count` same sum below sum( (start == 1)   &   (sma(start, n=11)[shiftindx] == 0), na.rm=true) 

---

and here benchmarks (before edit of adding `shiftindx`)  set.seed(7) (n in 10^(6:8)) {   cat("n is: ", n, "\n")   start <- round(rnorm(n, 0, 10))       print(system.time(     count <- sum(start == 1  &  sma(start, n=11) == 0, na.rm=true)   ))   cat("count ", count, "\n", rep("~", 14), "\n\n", sep="") }  ## output:   n is:  1e+06     user  system elapsed    0.059   0.021   0.081  count 485 ~~~~~~~~~~~~~~  n is:  1e+07     user  system elapsed    0.578   0.195   0.768  count 4889 ~~~~~~~~~~~~~~  n is:  1e+08     user  system elapsed    7.808   5.716  19.392  count 49737 ~~~~~~~~~~~~~~