How to extract time interval data from minute data in r - r

Question

I am trying to extract rows at 5 minute intervals from 1 minute data. My data looks like this:
structure(list(Date = structure(c(1509408000, 1509408000, 1509408000,
1509408000, 1509408000, 1509408000), class = c("POSIXct", "POSIXt"
), tzone = "UTC"), Time = structure(c(-2209021500, -2209021560,
-2209021620, -2209021680, -2209021740, -2209021800), class = c("POSIXct",
"POSIXt"), tzone = "UTC"), O = c(3674, 3675, 3674, 3675, 3675,
3675), H = c(3674, 3675, 3675, 3676, 3676, 3675), L = c(3673,
3674, 3674, 3674, 3675, 3675), C = c(3673, 3674, 3674, 3675,
3675, 3675)), row.names = c(NA, -6L), class = c("tbl_df", "tbl",
"data.frame"))
structure(list(Date = structure(c(1506902400, 1506902400, 1506902400,
1506902400, 1506902400, 1506902400), class = c("POSIXct", "POSIXt"
), tzone = "UTC"), Time = structure(c(-2209071300, -2209071360,
-2209071420, -2209071480, -2209071540, -2209071600), class = c("POSIXct",
"POSIXt"), tzone = "UTC"), O = c(3450, 3451, 3451, 3452, 3450,
3449), H = c(3451, 3451, 3451, 3452, 3452, 3451), L = c(3448,
3449, 3449, 3450, 3450, 3449), C = c(3448, 3451, 3450, 3451,
3452, 3450)), row.names = c(NA, -6L), class = c("tbl_df", "tbl",
"data.frame"))
I have looked at:
Create a time interval of 15 minutes from minutely data in R?
How to subset and extract time series by time interval in row
but none do exactly what I want. Maybe I could use this:
substr(t,15,16)=="00".
but I'm not sure how to combine it with filter.
Desired Output: find rows at 30 minute intervals:

Answer 1

You can extract rows with a minute-mark ending in 0 or 5 with
df[substr(format(df$Time, '%M'), 2, 2) %in% c(0, 5),]
# or
df[as.numeric(format(df$Time, '%M')) %% 5 == 0,]
# or
df[grep('[0|5]$', format(df$Time, '%M')),]
With filter:
library(dplyr)
df %>%
filter(substr(format(df$Time, '%M'), 2, 2) %in% c(0, 5))
# or
df %>%
filter(as.numeric(format(df$Time, '%M')) %% 5 == 0)