CODEWITHSUNDEEP
r
Jaitegh
Jaitegh

Reputation: 1

How to find the number of days for a certain criteria in a huge dataset?

I am working with a 30 year weather data and I have a list of temperature values:

tempC = c(-2,-3,-2,.......-5) These are temperature values of 11322 days(number of days in 30 years). Now, I want to find out how many days were there every year where temperature > 30degC. Year1 = 2001, Year30 = 2031

It's been driving me crazy as to how I would take into account the leap years and how can I get the correct answer.

Would highly appreciate any help! Thanks~

Upvotes: 0

Views: 138

Answers (1)

Ankur Sinha
Ankur Sinha

Reputation: 6639

Assuming you have the dates and can get the year, the syntax for it using dplyr would be:

library(dplyr)

df %>% group_by(year) %>% filter(tempC > 30)

where df is your dataframe, year is the column which has values like 2001,..,2030 and finally, tempC is the column with the values of temperature.

Look below to know how to extract the year from the dates, and to generate dates between Jan 1, 2001 to Dec 31, 2031 if required.

Sample dataframe:

  tempC       date
1    30 2012-12-29
2    27 2012-12-30
3    41 2012-12-31
4    22 2013-01-01
5    32 2013-01-02
6    44 2013-01-03
7    33 2013-01-04
8    22 2013-01-05

Getting year column using lubridate:

library(lubridate)

df$year <- year(ymd(df$date))

You now get:

  tempC       date year
1    30 2012-12-29 2012
2    27 2012-12-30 2012
3    41 2012-12-31 2012
4    22 2013-01-01 2013
5    32 2013-01-02 2013
6    44 2013-01-03 2013
7    33 2013-01-04 2013
8    22 2013-01-05 2013

Running the above dplyr code solution, final output:

  tempC date        year
  <dbl> <date>     <dbl>
1    41 2012-12-31  2012
2    32 2013-01-02  2013
3    44 2013-01-03  2013
4    33 2013-01-04  2013

In case you just have the values of temperatures and not dates, you can generate them using:

df$date <- seq(as.Date('2001-01-01'), by = 'day', len = 11322)

This will create dates between 1st Jan, 2001 until 31st Dec, 2031.

Upvotes: 1

Related Questions