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R Practice Questions for Matrix & Data Frames

1) Define a Matrix with names of the Columns & Rows defined at the time of Matrix definition

2) Do a row bind of a matrix(1:10 , 2 , 5 ) and another matrix( 11:15 , 1 ,5)

3) Create three vectors  x,y,z  with integers and each vector has 3 elements. 
      3.a ) Combine the three vectors to become a 3×3 matrix  'A'  where each column represents a vector.
      3.b) Change the row names to  a,b,c.

4) Show that the data structure created in the previous question is of 'Matrix' type 

5) Create a vector with 12 integers. Convert the vector to a 4*3 matrix  'B'  using  matrix(). 
      5.a) Please change the column names to x, y, z  & row names to  a, b, c, d.
      5.b) Also ensure that values are populated at 'Row' levels instead of 'Column' levels.

6) There exist a predefined 'Character Vector' in R called LETTERS , 
     this predefined variable LETTERS contain all the 26 English alphabets in Capital .
     6.a) Assign this predefined variable LETTERS to a new user defined variable 'Alpha_Mtrx'
     6.b) show the type of Data Structure for this new variable Alpha_Mtrx
     6.c) show the dimension of this new variable Alpha_Mtrx
     6.d) now use the 'dim()' function to change the dimension of Alpha_Mtrx to have 2 rows & 13 columns
     6.e) now show that the variable Alpha_Mtrx is a Matrix variable by using the function is.xxxxxx() 
     6.f) now change the names of the rows in the matrix to 'Row_1' & 'Row_2'

7) create a numeric matrix Num_Mtrx having values 1:20 with 4 rows & 5 columns.
      7.a) then create a new matrix from Num_Mtrx where rows in Num_Mtrx gets converted into columns

8) from the above numeric matrix Num_Mtrx , 
     8.a) create a numeric vector containing 5 elements where each element is sum of values in each column respectively
     8.b) create a numeric vector containing 4 elements where each element is sum of values in each row respectively

9) Add 10 to each numeric element in the Num_Mtrx and have the output stored in a new matrix variable

10) Flatten the Matrix Num_Mtrx into a 1 dimensional numeric vector 

11) extract from the Matrix Num_Mtrx , only the rows 2nd & 4th and store it in new Matrix

12) extract from the Matrix Num_Mtrx , only the columns 1st, 2nd & 4th and store it in new Matrix

13) extract from the Matrix Num_Mtrx , only the values in row 2 & columns 3rd & 5th.

14) can you create Data Frame from the matrix variable Num_Mtrx_DF

15) use the predefined character vector 'LETTERS' containing all English alphabets
       15.a) create a Data Frame named Letters_DF where it contains 2 columns
       15.b) where the first column is named as 'Even_Alphabets' & second column as 'Odd_Alphabets'
       15.c) and column 1 contains all the alphabets in even position ( 2nd , 4th , 6th .....)
       15.d) and column 2 contains all the alphabets in odd position ( 1st , 3rd , 5th .....)
       15.e) now extract the elements in the even rows of the column named 'Even_Alphabets' in the data frame created above
       15.f) now swap the position of the columns in the Dataframe ,1st column becomes 2nd column & vice versa

16) Create the dataframes to merge:
           buildings <- data.frame(location=c(1, 2, 3), name=c("building1", "building2", "building3"))
           data <- data.frame(survey=c(1,1,1,2,2,2), location=c(1,2,3,2,3,1), efficiency=c(51,64,70,71,80,58))

          The dataframes, buildings and data have a common key variable called, “location”. 
          Use the merge() function to merge the two dataframes by “location”, into a new dataframe, “buildingStats”.


Thank You & Happy Learning
Team Intiglide
@AUTHOR : Admin

Tags:Eco, Water, Air, Environment

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