R programming filtering data frame with date column

Question

For such Data Frame, I was trying to select some rows within a specific date range:

nasdaq=read.csv("nasdaq.csv")
head(nasdaq)

        Date Close.Price
1 2013-08-05     3692.95
2 2013-08-06     3665.77
3 2013-08-07     3654.01
4 2013-08-08     3669.12
5 2013-08-09     3660.11
6 2013-08-12     3669.95

what I have tried so far is:

chunk=subset(nasdaq,nasdaq$Date>=as.Date("2013-08-05") & nasdaq$Date<=as.Date("2018-08-03"))

Warning messages:

1: In eval(e, x, parent.frame()) :
  Incompatible methods ("Ops.factor", "Ops.Date") for ">="
2: In eval(e, x, parent.frame()) :
  Incompatible methods ("Ops.factor", "Ops.Date") for "<="

I have also tried...

 chunk=nasdaq[nasdaq$Date>=as.Date("2013-08-05") & nasdaq$Date<=as.Date("2018-08-03"),]

Warning messages:

1: In `[.data.frame`(nasdaq, nasdaq$Date >= as.Date("2013-08-05") &  :
  Incompatible methods ("Ops.factor", "Ops.Date") for ">="
2: In `[.data.frame`(nasdaq, nasdaq$Date >= as.Date("2013-08-05") &  :
  Incompatible methods ("Ops.factor", "Ops.Date") for "<="

I have tried both of above without as.Date function but doesn't work, Please advise where I may be going wrong?

you have read in the dates as a factor by not doing read.csv("nasdaq.csv", stringsAsFactors = F). That is step 1. — cylondude
– cylondude, Commented Aug 15, 2018 at 22:45

neilfws · Accepted Answer · 2018-08-15 22:47:37Z

3

The warning message tells you the issue. Column Date in your data frame is a factor, not a date. This is because you did not specify stringsAsFactors = FALSE in read.csv (then Date would be a character).

There are several ways to fix this. You can convert to dates after reading the data:

nasdaq$Date <- as.Date(nasdaq$Date, "%Y-%m-%d")

Or you can use the colClasses argument when reading the file:

nasdaq <- read.csv("nasdaq.csv", header = TRUE, colClasses = c("Date", "numeric"))

Or you could use readr::read_csv, which will recognise that the column contains dates.

answered Aug 15, 2018 at 22:47

neilfws

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Suhas Hegde · Accepted Answer · 2018-08-15 22:46:27Z

0

This should work for you,

library(dplyr)
library(lubridate)

# dummmy data
test_data <- data.frame(
  Date = ymd(c("2013-08-05","2013-08-06 ","2013-08-07")),
  Close.Price = c(3692.95,3665.77,3654.01)
)

test_data %>%
  filter(Date >= ymd("2013-08-05") & Date <= ymd("2013-08-07"))

        Date Close.Price
1 2013-08-05     3692.95
2 2013-08-06     3665.77
3 2013-08-07     3654.01

answered Aug 15, 2018 at 22:46

Suhas Hegde

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SmitM · Accepted Answer · 2018-08-15 22:46:40Z

0

You need to specify the format of the date string in the as.Date() function before you can use it in the subset function

nasdaq$Date <- as.Date(nasdaq$Date, format = "%Y-%m-%d")
chunk <- subset(nasdaq,nasdaq$Date >= "2013-08-05" & nasdaq$Date <= "2018-08-03")

answered Aug 15, 2018 at 22:46

SmitM

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