CSC121.pdf - DataCamp Intro to R Tuesday 3:53 PM...

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When you print some_vector, there will be title labels above each element notes (some_vector) <- c("name1","name2") assigns names to elements of some_vector Always try to avoid code duplication Adding two vectors adds respective elements sum (some_vector) adds all elements of a vector positive_vector <- some_vector > 0 will create vector with boolean values (T/F) indicating whether each element passes the conditio n (elem > 0) another_vector[boolean_vector] will only return elements that correspond with TRUE in boolean vector rowSums(matrix) adds all elements of row and makes new column matrix DataCamp: Intro to R Tuesday, February 21, 2017 3:53 PM CSC121 Page 1
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Data type that stores categorical variables Important because R needs to know whether var is categorical or continuous (numerical) Create vector ( category_vector ) with all categories aka factor levels 1. factor_category_vector <- factor (category_vector) encodes vector as a factor 2. Setting Up Factors # of categories in a factor = # of "factor levels" Recall: nominal means no implied order, ordinal means natural order exists > survey_vector <- c("M", "F", "F", "M", "M") > factor_survey_vector <- factor(survey_vector) > levels(factor_survey_vector) <- c("Female", "Male") Note: "Female" comes first because F is alphabetically before M, so it will begin naming from F first When assigning levels to a factor (changing names of categories), your level vector c("name1","name2") should correspond to the alphabetical order of your factor summary(some_vector) that is NOT factorized, will only give you info about what kind of string it is summary(factor_some_vector) allows R to tally up occurences of each factor level factor() creates unordered factor Need to add two arguments to make it ordinal: ordered and levels factor(some_vector, ordered = TRUE, levels = c("lev1", "lev2" ...)) where levels allows us to give values of factor in correct order Now printing the factor vector tells us levels, and summary tells us number of occurences Ordered Factors Elements of an ordered factor can be tested for inequalites (> = <), resulting in T/F Factors Tuesday, February 21, 2017 3:53 PM CSC121 Page 2
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