Creating Matrices using Data Frames - English

Questions posted on ST Forums:

• TRUE MATRIX MULTIPLICATION

  Hi,I have a doubt regarding true matrix multiplication.matrixA as per the video - 45,49,47,22,21,14,12,13,14 subdata <- captaincy[1:3,c("played","won","lost")] > matrixA <- as.matrix(subdata)> print(matrixA) played won lost [1] 45 22 12 [2] 49 21 13 [3] 47 14 14 matrixB - my own values <- c(1,0,1,1,0,1,0,1,0)> matrixB <- matrix(values,nrow=3,ncol=3,byrow=FALSE) print(matrixB) [,1] [,2] [,3] [1,] 1 1 0[2,] 0 0 1 [3,] 1 1 0 true matric multiplication - matrixA %*% matrixB - THE RESULTS I AM GETTING  ARE - [,1] [,2] [,3] 1 57 57 22 2 62 62 21 3 61 61 14 THE RESULTS SHOWN IN THE VIDEO - (with matrixB  values of his own <-c(1,0,0,0,1,0,0,0,1)) [,1] [,2] [,3] 1 45 22 12 2 49 21 13 3 47 14 14  Could you please explain where am I  going wrong ? Thanks!

  07-08M 50-60S PRANATHI_KALANGI
  
  
  Answer last updated on: Sept. 24, 2024, 9:01 a.m.

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• by enter the command as given in tutorial matrix didn't make

  print(matrixB)Error in print(matrixB) : object 'matrixB' not foundTHE ABOVE LINE SHOWN BY R STUDIO WHILE MAKING MATRIX.

  03-04M 10-20S tanishagoyal
  
  
  Answer last updated on: Aug. 17, 2021, 4:14 p.m.

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• Assignment

  matrixB=matrix(nrow=4,ncol=2,data = c(9,10,11,12,13,14,15,16))print(matrixB)     [,1] [,2][1,]    9   13[2,]   10   14[3,]   11   15[4,]   12   16Sir i have doubt if i type the above coding i am getting the above solution but the assignment was to create two vectors so i have the coding as x=c(9,10,11,12)y=c(13,14,15,16)matrixB=matrix(nrow=4,ncol=2,x,y) print(matrixB)     [,1] [,2][1,]    9   10[2,]   11   12[3,]    9   10[4,]   11   12i am getting like above solution , pls correct me sir

  10-11M 50-60S kajalmeena
  
  
  Answer last updated on: Aug. 15, 2021, 11:49 a.m.

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• Assignment

  Is an assignment, for submission or practice? if it is for submission so how to submit?

  09-10M 30-40S shiksha_saxena
  
  
  Answer last updated on: June 17, 2020, 1:16 p.m.

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• Matrix multiplication

  what is the difference between matrixA*matrixBmatrixA%*%matrixB

  08-09M 20-30S bindukannan
  
  
  Answer last updated on: June 17, 2020, 12:11 p.m.

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• what is %*%

  what operation exactly perform ? 

  08-09M 10-20S nameisbond7@gmail.com
  
  
  Answer last updated on: May 24, 2020, 5:12 p.m.

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• Assignment

  Check for the assignment sirx=c(9,10,11,12) y=c(13,14,15,16) matrixA=matrix(x,y,nrow = 4,ncol = 2) print(matrixA) [,1] [,2] [1,] 9 10 [2,] 11 12 [3,] 9 10 [4,] 11 12

  09-10M 40-50S Alamu
  
  
  Answer last updated on: May 16, 2020, 3:32 p.m.

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• subdata

  Sir in the current vidoe "subdata" you used small letter for data but in the previous lecture indexing and slicing for the subset you used " "subData". Is both correct sir

  06-07M 20-30S Alamu
  
  
  Answer last updated on: May 16, 2020, 3:29 p.m.

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• Print command

  When should print command be used for displaying output and when is it not required? In this video, the author is using print(matrixB) command to obtain matrix output in Console window.However, in assignment solution, output is being obtained even without print command.How is it so?

  06-07M 40-50S dsouzafleur@gmail.com
  
  
  Answer last updated on: April 29, 2020, 5:31 p.m.

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• MATRICES- Creating 3 X 3 IDENTITY MATRIX

  I have encountered a problem in creating 3 x 3 identity matrix. #create a matrix of 3 rows and 3 columns using the following codevalues <- c(1,0,0,0,1,0,0,0,1)matrixB <- as.matrix(values, nrow = 3, ncol = 3, byrow = TRUE) print(matrixB)But output i am getting isprint(matrixB)      [,1] [1,]    1 [2,]    0 [3,]    0 [4,]    0 [5,]    1 [6,]    0 [7,]    0 [8,]    0 [9,]    1Please tell me the solution..Thanks.

  06-07M 30-40S annieahuja89@gmail.com
  
  
  Answer last updated on: April 28, 2020, 2:54 p.m.

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• Creating Matrices using Data Frames

  Is there an option to create matrix directly without creating a vector?

  05-06M 50-60S angaiaruvi@gmail.com
  
  
  Answer last updated on: April 28, 2020, 12:39 p.m.

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