CODEWITHSUNDEEP
rdplyr
Caitlin
Caitlin

Reputation: 37

Filter a data frame by two conditions in R

I have a data frame that contains the highest and lowest temperature in a given year by Climate Station - All.Stations dataset: 

Station.Name    Year    Month   Day TMAX    TMIN
GRAND MARAIS    1942    7       28    82      60
GRAND MARAIS    1962    3       17    42      22
LEECH LAKE      1956    7       3     72      50
ALBERT LEA 3 SE 1998    1       25    25      15
TWO HARBORS     1933    5       20    77      42
ARGYLE          1922    9       13    NA      NA

I also have a data frame of complete years by Climate Station (i.e., these are the years where I have data for every day in the year) - complete.years dataset: 

Station.Name    Year
DULUTH          1904
AGASSIZ REFUGE  1995
LEECH LAKE      1956
GRAND MARAIS    1942
LEECH LAKE      1994

I want to filter the first data frame to only the data where Station Name and Year exist and match in the second data frame.

The correct results would be: 

Station.Name    Year TMAX
GRAND MARAIS    1942   82
LEECH LAKE      1956   72

Here's what I've got so far, using dplyr:

Max.Tempurature <- All_Stations %>% 
  group_by(Station.Name, Year) %>%
  select(Station.Name, Year, TMAX) %>%
  filter(min_rank(desc(TMAX)) <= 1) %>%
  filter((Year %in% complete.years$Year & Station.Name %in% complete.years$Station.Name))

I can filter by both Year and Station.Name, but that searches the whole data frame for matches.

How do I filter by Station.Name and Year existing in the same observation?

Upvotes: 3

Views: 84

Answers (2)

markus
markus

Reputation: 26333

Or with merge

cols <- c('Station.Name', 'Year', 'TMAX')
merge(All.Stations[cols], complete.years, all.x = FALSE)
#  Station.Name Year TMAX
#1 GRAND MARAIS 1942   82
#2   LEECH LAKE 1956   72

data

All.Stations <- structure(list(Station.Name = c("GRAND MARAIS", "GRAND MARAIS", 
"LEECH LAKE", "ALBERT LEA 3 SE", "TWO HARBORS", "ARGYLE"), Year = c(1942L, 
1962L, 1956L, 1998L, 1933L, 1922L), Month = c(7L, 3L, 7L, 1L, 
5L, 9L), Day = c(28L, 17L, 3L, 25L, 20L, 13L), TMAX = c(82L, 
42L, 72L, 25L, 77L, NA), TMIN = c(60L, 22L, 50L, 15L, 42L, NA
)), .Names = c("Station.Name", "Year", "Month", "Day", "TMAX", 
"TMIN"), class = "data.frame", row.names = c(NA, -6L))

complete.years <- structure(list(Station.Name = c("DULUTH", "AGASSIZ REFUGE", "LEECH LAKE", 
"GRAND MARAIS", "LEECH LAKE"), Year = c(1904L, 1995L, 1956L, 
1942L, 1994L)), .Names = c("Station.Name", "Year"), class = "data.frame", row.names = c(NA, 
-5L))

Upvotes: 1

akrun
akrun

Reputation: 886938

We can do an inner_join

library(dplyr)
inner_join(All.Stations[c(1, 2, 5)], complete.years)
#   Station.Name Year TMAX
#1 GRAND MARAIS 1942   82
#2   LEECH LAKE 1956   72

data

All.Stations <- structure(list(Station.Name = c("GRAND MARAIS", "GRAND MARAIS", 
"LEECH LAKE", "ALBERT LEA 3 SE", "TWO HARBORS", "ARGYLE"), Year = c(1942L, 
1962L, 1956L, 1998L, 1933L, 1922L), Month = c(7L, 3L, 7L, 1L, 
5L, 9L), Day = c(28L, 17L, 3L, 25L, 20L, 13L), TMAX = c(82L, 
42L, 72L, 25L, 77L, NA), TMIN = c(60L, 22L, 50L, 15L, 42L, NA
)), class = "data.frame", row.names = c(NA, -6L))

complete.years <- structure(list(Station.Name = c("DULUTH", 
    "AGASSIZ REFUGE", "LEECH LAKE", 
"GRAND MARAIS", "LEECH LAKE"), Year = c(1904L, 1995L, 1956L, 
1942L, 1994L)), class = "data.frame", row.names = c(NA, -5L))

Upvotes: 2

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