A collection of R functions that I found helpful. Some of these functions require the tidyverse package.

Getting info on variables

  • str(my_varb) - displays the content of an R object (i.e., any variable)
  • class(my_varb) - displays the class of an R object (i.e., any variable)

Getting info on data sets

  • head(my_data) - displays the first six lines of a data set
  • names(my_data) - displays the names of the variables within a data set
  • summarize(mydata)- summarizes data into single row of values
  • count() - lets you count the unique values of one or more variables within each group of a categorical variable
    • ex. my_data %>% count(large_cats)

Manipulating data sets

  • filter(my_data, condition) - keeps the data that matches the condition. Works on rows.

    • ex. Assuming you have a data set my_data that has a variable named num_cats you could filter out all rows that saw no cats with the following code filter(my_data, num_cats>0)
  • select(my_data, vars) - can return a specified subset of the data or remove a set of variables from the data. Works on columns.

    • ex. select(my_data, A, B, C) - selects the variables A, B, C from my_data data set
    • ex. select(my_data, -B) - remove’s variable C from my_data data set
  • mutate() - appends a new column of data to the original data set

    • ex. Assuming you have a data set my_data that had a variable named num_cats you could add a variable named cats_per_hour with the following code: my_data %>% mutate(cats_per_hour = (num_cats/60))
  • mutate_if(if_statement, mutation) - affects only the columns that satisfy the if statement

  • mutate_at(c(col1, col2, col3), mutation) - edits the specific columns with the mutation

  • group_by(my_data, var) - groups the data according to different “levels” of a categorical variable of your choice.

  • relevel(fct_vect, new-reference-level) - the levels of a factor are re-ordered so that the level specified by new-reference-levelis first and the others are moved down

  • fct_infreq(cat_varb) - factor order so that the category with the most observational units is the reference variable

  • fct_rev(cat_varb) - reverses the order of the factor levels

  • fct_recode(cat_varb) - manually choose what you want the reference level to be

    • ex. from R documentation:

    • x <- factor(c("apple", "bear", "banana", "dear"))
      fct_recode(x, fruit = "apple", fruit = "banana")
      
  • factor(cat_varb) - factor levels are arranged in alphabetical order

Standardizing Data

Uses the mutate_at and scale function to standardize the data

my_data_standard <- my_data %>% 
                     mutate_at(vars("var1", "var2", "var3", "var4"), funs(scale))  

Miscellaneous

  • cor(data_object$xvariable, data_object$yvariable) - calculates the correlation (strength of the linear relationship) between two quantitative variables

    • Recall correlation is the standardized (is on the domain of [-1,1]) version of the covariance
  • dim(my_data) - spits out the dimensionality — i.e. how big – a table or dataset is