CODEWITHSUNDEEP
rdplyrtidyverselubridate
zizamuft
zizamuft

Reputation: 93

how to get specific date in time series in r

I want to make a forecast project from a time series dataframe. but, the time span is too big. then, I have this column in dataframe from a time series data frame.

Date
2010-06-29
2010-06-30
2010-07-01
2010-07-02

how can I change it so that it only shows every 7 days?

Date
2010-06-29
2010-07-05
2010-07-12
2010-07-19
etc

Upvotes: 0

Views: 326

Answers (2)

GuedesBF
GuedesBF

Reputation: 9858

Daniel's answer is very simple and direct. However, it will return only data from a specified weekday, which could lead to biased results depending on the nature of your data.

You can create an index of weekdays that is balanced with random sampling of weekdays:

# example data
df <- data.frame(date = seq.Date(from = ymd("2021/01/01"), 
                                 to = ymd("2021/12/31"),
                                 by = "day"))

#create index by sampling weekdays randomly

set.seed(1)
index<-replicate(floor(nrow(df)/7), {sample(unique(df$weekday), replace = FALSE)}) %>% 
        as.vector()

#subsetting to a 7-fold smaller dataset

library(dplyr)

output<-df %>% filter(weekdays(date)==index)

#checking table of weekdays in the final dataset

table(output$weekday)

   Friday    Monday  Saturday    Sunday  Thursday   Tuesday Wednesday 
       13         6         5         9         8        10         6

Upvotes: 0

Arik Pamnani
Arik Pamnani

Reputation: 441

dataframe.new = dataframe[seq(1, nrow(dataframe), 7),]

seq documentation - https://www.rdocumentation.org/packages/base/versions/3.6.2/topics/seq

basically, seq(1, 100, 7) will generate - 1, 8, 15, ...

Upvotes: 1

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