Page 211 - Data Science class 11
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tan(x) #Tangent of x
               acos(x) # arc-cosine of x
               asin(x) # arc-sine of x

               atan(x) #arc-tangent of x

            c.  Other mathematical functions
               abs(x) # absolute value of x
               sqrt(x) # square root of x


            6.4 VariaBLes

            Generally, while doing programming in any programming language, you need to use various variables to store
            various types of information. Variables are nothing but reserved memory locations to store values. This means that,
            when you create a variable you reserve some space in memory.
            For moving the concept of variables before Script programming, the author should be consulted.

            You may want to save data of various data types such as characters, wide characters, integers, floating points, double
            floating points, Boolean, and so on.
            Wide  characters  (It  is  a  computer  character  datatype  that  generally  has  a  size  greater  than  the  traditional  8-bit
            character.

            Based on the data type of a variable, the operating system allocates memory and decides what can be stored in the
            reserved memory.

            6.4.1 Variable names or identifiers

            A variable can have a short name (like x and y) or a more descriptive name (age, studentname, total_area).
            Rules for writing variables in R are:
               • A variable name must start with a letter and can be a combination of letters, digits, period(.) and underscore(_). If it
              starts with a period(.), it cannot be followed by a digit.
               • A variable name cannot start with a number or underscore (_)
               • Variable names are case-sensitive (as a result,length, Length, LENGTH  are all distinct variables).
               • Reserved keywords cannot be used as variables (TRUE, FALSE, NULL, if...)
               • Special characters are not allowed.
            Examples of Legal variable names

                1.  myvar <- "   Sapna"
                2.  my_var <- "  Sapna"
                3.  myVar <- "  Sapna"
                4.  MYVAR <- "  Sapna"

                5.  myvar2 <- "  Sapna"
                6.  .myvar <-   Sapna
            Examples of Illegal variable names:
                1.  2myvar <- "  Sapna"

                    Because it starts with a number.
                2.  my-var <- "  Sapna"

                    Because it contains – instead of probably _.
                                                                                         Programming with R    209
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