Import your data

data(flights)

flights %>% skimr::skim()
Data summary
Name Piped data
Number of rows 336776
Number of columns 19
_______________________
Column type frequency:
character 4
numeric 14
POSIXct 1
________________________
Group variables None

Variable type: character

skim_variable n_missing complete_rate min max empty n_unique whitespace
carrier 0 1.00 2 2 0 16 0
tailnum 2512 0.99 5 6 0 4043 0
origin 0 1.00 3 3 0 3 0
dest 0 1.00 3 3 0 105 0

Variable type: numeric

skim_variable n_missing complete_rate mean sd p0 p25 p50 p75 p100 hist
year 0 1.00 2013.00 0.00 2013 2013 2013 2013 2013 ▁▁▇▁▁
month 0 1.00 6.55 3.41 1 4 7 10 12 ▇▆▆▆▇
day 0 1.00 15.71 8.77 1 8 16 23 31 ▇▇▇▇▆
dep_time 8255 0.98 1349.11 488.28 1 907 1401 1744 2400 ▁▇▆▇▃
sched_dep_time 0 1.00 1344.25 467.34 106 906 1359 1729 2359 ▁▇▇▇▃
dep_delay 8255 0.98 12.64 40.21 -43 -5 -2 11 1301 ▇▁▁▁▁
arr_time 8713 0.97 1502.05 533.26 1 1104 1535 1940 2400 ▁▃▇▇▇
sched_arr_time 0 1.00 1536.38 497.46 1 1124 1556 1945 2359 ▁▃▇▇▇
arr_delay 9430 0.97 6.90 44.63 -86 -17 -5 14 1272 ▇▁▁▁▁
flight 0 1.00 1971.92 1632.47 1 553 1496 3465 8500 ▇▃▃▁▁
air_time 9430 0.97 150.69 93.69 20 82 129 192 695 ▇▂▂▁▁
distance 0 1.00 1039.91 733.23 17 502 872 1389 4983 ▇▃▂▁▁
hour 0 1.00 13.18 4.66 1 9 13 17 23 ▁▇▇▇▅
minute 0 1.00 26.23 19.30 0 8 29 44 59 ▇▃▆▃▅

Variable type: POSIXct

skim_variable n_missing complete_rate min max median n_unique
time_hour 0 1 2013-01-01 05:00:00 2013-12-31 23:00:00 2013-07-03 10:00:00 6936

Create Data frame functions

Example 1: count columns

code snippets

ncol_num <- flights %>%
    
    # Select a type of variables
    select(where(is.numeric)) %>%
    
    # Count columns
    ncol()

ncol_num
## [1] 14

Turn them into a function

count_ncol_numeric <- function(.data) {
    
    # Body
    ncol_num <- .data %>%
    
        # Select a type of variables
        select(where(is.numeric)) %>%
    
        # Count columns
        ncol()
    
    # Return new vatible
    return(ncol_num)
    
}

flights %>% count_ncol_numeric()
## [1] 14
flights %>% .[1:10, 1:5] %>% count_ncol_numeric()
## [1] 5
flights %>% .[1:10, -1:-13] %>% count_ncol_numeric()
## [1] 4

Adding arguments for details of operation

count_ncol_type <- function(.data, type_data = "numeric") {
    
    # If statement for type of variables
    if(type_data == "numeric") {
        
        # Body
        ncol_type <- .data %>%
    
            # Select a type of variables
            select(where(is.numeric)) %>%
    
            # Count columns
            ncol()
        
    } else if(type_data == "character") {
        
        # Body
        ncol_type <- .data %>%
    
             # Select a type of variables
            select(where(is.character)) %>%
    
             # Count columns
            ncol()
        
    }
    
    
    # Return new vatible
    return(ncol_type)
    
}

flights %>% count_ncol_type()
## [1] 14
flights %>% count_ncol_type(type_data = "character")
## [1] 4
flights %>% .[1:10, 1:5] %>% count_ncol_type(type_data = "character")
## [1] 0

Example 2: count rows

code snippets

nrow_num <- flights %>%
    
    # filter rows that meet a condition
    filter(carrier == "UA") %>%
    
    # Count rows
    nrow()

nrow_num
## [1] 58665

Turn them into a function

count_num_flights_by_carrier <- function(.data, carrier_name) {
    
    # Body
    nrow_num <- .data %>%
        
        # filter rows that meet a condition
        filter(carrier == carrier_name) %>%
        
        # Count rows
        nrow()    
    
    # Return the new varible
    return(nrow_num)
}

flights %>% .[1:10, "carrier"] %>% 
count_num_flights_by_carrier(carrier_name = "AA")
## [1] 2
flights %>% .[1:10, "carrier"] %>% count_num_flights_by_carrier(carrier_name = "AA")
## [1] 2

Example 3: count rows

data <- read_csv("../00_data/MyData.csv")
## Rows: 882 Columns: 69
## ── Column specification ────────────────────────────────────────────────────────
## Delimiter: ","
## chr  (22): EXPID, PEAKID, SEASON_FACTOR, HOST_FACTOR, ROUTE1, ROUTE2, NATION...
## dbl  (17): YEAR, SEASON, HOST, SMTDAYS, TOTDAYS, TERMREASON, HIGHPOINT, CAMP...
## lgl  (27): ROUTE3, ROUTE4, SUCCESS1, SUCCESS2, SUCCESS3, SUCCESS4, ASCENT3, ...
## date  (3): BCDATE, SMTDATE, TERMDATE
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.
data
## # A tibble: 882 × 69
##    EXPID     PEAKID  YEAR SEASON SEASON_FACTOR  HOST HOST_FACTOR ROUTE1   ROUTE2
##    <chr>     <chr>  <dbl>  <dbl> <chr>         <dbl> <chr>       <chr>    <chr> 
##  1 EVER20101 EVER    2020      1 Spring            2 China       N Col-N… <NA>  
##  2 EVER20102 EVER    2020      1 Spring            2 China       N Col-N… <NA>  
##  3 EVER20103 EVER    2020      1 Spring            2 China       N Col-N… <NA>  
##  4 AMAD20301 AMAD    2020      3 Autumn            1 Nepal       SW Ridge <NA>  
##  5 AMAD20302 AMAD    2020      3 Autumn            1 Nepal       SW Ridge <NA>  
##  6 AMAD20303 AMAD    2020      3 Autumn            1 Nepal       SW Ridge <NA>  
##  7 AMAD20304 AMAD    2020      3 Autumn            1 Nepal       SW Ridge <NA>  
##  8 AMAD20305 AMAD    2020      3 Autumn            1 Nepal       SW Ridge <NA>  
##  9 AMAD20306 AMAD    2020      3 Autumn            1 Nepal       SW Ridge <NA>  
## 10 AMAD20307 AMAD    2020      3 Autumn            1 Nepal       SW Ridge <NA>  
## # ℹ 872 more rows
## # ℹ 60 more variables: ROUTE3 <lgl>, ROUTE4 <lgl>, NATION <chr>, LEADERS <chr>,
## #   SPONSOR <chr>, SUCCESS1 <lgl>, SUCCESS2 <lgl>, SUCCESS3 <lgl>,
## #   SUCCESS4 <lgl>, ASCENT1 <chr>, ASCENT2 <chr>, ASCENT3 <lgl>, ASCENT4 <lgl>,
## #   CLAIMED <lgl>, DISPUTED <lgl>, COUNTRIES <chr>, APPROACH <chr>,
## #   BCDATE <date>, SMTDATE <date>, SMTTIME <chr>, SMTDAYS <dbl>, TOTDAYS <dbl>,
## #   TERMDATE <date>, TERMREASON <dbl>, TERMREASON_FACTOR <chr>, …

code snippets

Use the filter() function to select rows that meet a condition. Refer to Chapter 5.2 Filter rows with filter()

nrow_num <- data %>%
    
    filter(PEAKID == "EVER") %>%
    nrow()

nrow_num
## [1] 189

Turn them into a function

PEAKID_by_HOST <- function(data, HOST) {
    
    nrow_num <- data %>%
    
    filter("PEAKID" == HOST) %>%
    nrow()

return(nrow_num)
}

data %>% .[1:10, "HOST"] %>% 
PEAKID_by_HOST (HOST = "AA")
## [1] 0