The filter() function in R is used to extract subsets of rows from a data frame. It is similar to the existing subset() function in R but is quite a bit faster in my experience.
The filter() function takes a data frame and a logical sequence as input and returns a new data frame containing only the rows where the logical sequence is true. For example, the following code would extract the rows of the chicago data frame where the levels of PM2.5 are greater than 30:
chic.f <- filter(chicago, pm25tmean2 > 30)
The filter() function can also be used to extract rows where multiple conditions are met. For example, the following code would extract the rows of the chicago data frame where the levels of PM2.5 are greater than 30 and the temperature is greater than 80 degrees Fahrenheit:
chic.f <- filter(chicago, pm25tmean2 > 30 & tmpd > 80)
The filter() function is a powerful tool for extracting subsets of data frames. It is quick and easy to use, and it can be used to extract rows where multiple conditions are met.
Examples of how to use the filter() function
- Extract the rows where the city is "Chicago" and the temperature is greater than 80 degrees Fahrenheit:
chic.f <- filter(chicago, city == "Chicago" & tmpd > 80)
- Extract the rows where the PM2.5 levels are between 30 and 50:
chic.f <- filter(chicago, pm25tmean2 >= 30 & pm25tmean2 <= 50)
- Extract the rows where the date is between January 1, 1998 and December 31, 1998:
chic.f <- filter(chicago, date >= as.Date("1998-01-01") & date <= as.Date("1998-12-31"))
