# How to improve the speed of nest for loops

I am relatively new to R. I have created code to review a dataframe and identify rows of data based on specific conditions, and mark those rows with a 1 and the column "check". The code works exactly how I have intended it to with the test data. My problem is the real dataset is 1 million plus rows, and while it works, it is way too slow. I would appreciate help in improving the efficiency of this code.

``````#create test data
alarm <- c(0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0)
setpoint <- c(10,10,10,10,10,10,10,10,8,8,9,8,8,10,10,10,10,10,10,10,10,10,10,10,8,10,10,8,10,10,10)

temp <- data.frame(alarm, setpoint)

#create a new column to capture if there is any changes to setpoint after any alarm
temp\$check <- ""

#review everyrow in dataframe
for(i in 1:nrow(temp)){
cat(round(i/nrow(temp)*100,2),"%    \r") # prints the percentage complete in realtime.
if(temp\$alarm[i]==1 && temp\$setpoint[i] >= 10){
#for when alarm has occurred and the setpoint is 10 or above review the next 5 rows
for(j in 0:5){
if(temp\$setpoint[i] != temp\$setpoint[i+j]){
#for when there has been a change in the setpoint
for(q in 0:10){
if(temp\$setpoint[i] != temp\$setpoint[i+q]){
temp\$check[i+q]<-'1'
if(temp\$setpoint[i+q] != (temp\$setpoint[i+q+1])){break}
}
}
}
}
}
}

> print(temp)
alarm setpoint check
1      0       10
2      0       10
3      0       10
4      0       10
5      0       10
6      0       10
7      1       10
8      1       10
9      0        8     1
10     0        8     1
11     0        9
12     0        8
13     0        8
14     0       10
15     0       10
16     0       10
17     1       10
18     0       10
19     0       10
20     0       10
21     0       10
22     1       10
23     0       10
24     0       10
25     0        8     1
26     0       10
27     0       10
28     0        8
29     0       10
30     0       10
31     0       10
``````

Would you be able to provide the conditions to apply in the form of a description in plain english?
I am suspicious of your code which loops j within a loop of j ...

Code updated second j replaced with q

Is that a no to the request for a plain english description ?

Logic applied to the dataset

Review every row in the data set. If alarm is triggered and the setpoint is greater than 10 then review the next 5 rows of data. In that 5 rows, check if there is any changes to the setpoint , and if there is a change continue to review for 10 rows, and capture the occasions that setpoint is different to the original alarm point (to a maximum of 10 rows). If during this 10 minutes of review there is another change in setpoint the loop is broken.

The slowest functionality your code employs is printing out the progress of your process. You can easily gain the biggest performance increase by doing that less.
There are also occasions where your code seems to repeat a calculation over a row it has done an equivalent calculation for (unless I am mistaken), therefore I added additional skip checks.
The new code performs as the old code in terms of results, though if there are edge cases that I've not considered that your example data doesnt cover this may be misleading.
For convenience and to facilitate benchmarking, I use a function to generate more of your example data.

``````
make_new_data <- function(reps) {
temp <- data.frame(
alarm = c(0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0),
setpoint = c(10, 10, 10, 10, 10, 10, 10, 10, 8, 8, 9, 8, 8, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 8, 10, 10, 8, 10, 10, 10)
)

# create a new column to capture if there is any changes to setpoint after any alarm
temp\$check <- ""
temp
do.call(rbind,rep(list(temp),reps))
}

newdata<-make_new_data(200)

do_with_skips <- function(temp) {
temp\$beenhere <- ""
# review everyrow in dataframe
for (i in 1:nrow(temp)) {
cat(round(i / nrow(temp) * 100, 2), "%    \r") # prints the percentage complete in realtime.
if (temp\$alarm[i] == 1 && temp\$setpoint[i] >= 10) {
# for when alarm has occurred and the setpoint is 10 or above review the next 5 rows
for (j in 0:5) {
if (temp\$setpoint[i] != temp\$setpoint[i + j]) {
if (temp\$beenhere[i + j] == "1") {
break
}
temp\$beenhere[i + j] <- paste0(temp\$beenhere[i + j], "1")
# for when there has been a change in the setpoint
for (q in 0:10) {
if (temp\$setpoint[i] != temp\$setpoint[i + q]) {
if (temp\$check[i + q] == "1") {
break
}
temp\$check[i + q] <- paste0(temp\$check[i + q], "1")
if (temp\$setpoint[i + q] != (temp\$setpoint[i + q + 1])) {
break
}
}
}
}
}
}
}
temp\$beenhere <- NULL
temp
}

do_with_skips_less_print <- function(temp) {
temp\$beenhere <- ""
# review everyrow in dataframe
for (i in 1:nrow(temp)) {
if(i %% 100==0)
cat(round(i / nrow(temp) * 100, 2), "%    \r") # prints the percentage complete in realtime.
if (temp\$alarm[i] == 1 && temp\$setpoint[i] >= 10) {
# for when alarm has occurred and the setpoint is 10 or above review the next 5 rows
for (j in 0:5) {
if (temp\$setpoint[i] != temp\$setpoint[i + j]) {
if (temp\$beenhere[i + j] == "1") {
break
}
temp\$beenhere[i + j] <- paste0(temp\$beenhere[i + j], "1")
# for when there has been a change in the setpoint
for (q in 0:10) {
if (temp\$setpoint[i] != temp\$setpoint[i + q]) {
if (temp\$check[i + q] == "1") {
break
}
temp\$check[i + q] <- paste0(temp\$check[i + q], "1")
if (temp\$setpoint[i + q] != (temp\$setpoint[i + q + 1])) {
break
}
}
}
}
}
}
}
temp\$beenhere <- NULL
temp
}

do_without_skips <- function(temp) {
for (i in 1:nrow(temp)) {
cat(round(i / nrow(temp) * 100, 2), "%    \r") # prints the percentage complete in realtime.
if (temp\$alarm[i] == 1 && temp\$setpoint[i] >= 10) {
# for when alarm has occurred and the setpoint is 10 or above review the next 5 rows
for (j in 0:5) {
if (temp\$setpoint[i] != temp\$setpoint[i + j]) {
# for when there has been a change in the setpoint
for (q in 0:10) {
if (temp\$setpoint[i] != temp\$setpoint[i + q]) {
temp\$check[i + q] <- "1"
if (temp\$setpoint[i + q] != (temp\$setpoint[i + q + 1])) {
break
}
}
}
}
}
}
}
temp
}

library(bench)
mark(do_with_skips_less_print(newdata),
do_with_skips(newdata),
do_without_skips(newdata),
iterations = 30)
``````
``````# A tibble: 3 x 13
expression                            min  median `itr/sec` mem_alloc `gc/sec` n_itr  n_gc total_time result memory
<bch:expr>                        <bch:t> <bch:t>     <dbl> <bch:byt>    <dbl> <int> <dbl>   <bch:tm> <list> <list>
1 do_with_skips_less_print(newdata)  58.3ms  68.2ms     14.3     47.6MB    11.9     30    25      2.09s <df>   <Rprofmem>
2 do_with_skips(newdata)            272.6ms 299.6ms      3.30    47.6MB     2.86    30    26      9.09s <df>   <Rprofmem>
3 do_without_skips(newdata)         324.7ms 356.7ms      2.70    90.1MB     3.78    30    42     11.12s <df>   <Rprofmem>``````

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