In R programming, a matrix can be scaled and centred using scale() function. But, there is no in-built function to transform the scaled matrix back to the original matrix. In this article, we’ll learn to transform the scaled matrix back to the original matrix using some simple computations.
Using Matrix Attributes
Attributes of the scaled matrix can be used to unscale the matrix back to its original matrix.
# Create matrix mt <- matrix(c(1:20), ncol = 5) # Print original matrix cat("Original matrix:\n") print(mt) # Scale the matrix scaled.mt <- scale(mt) # Print Scaled matrix cat("Scaled matrix:\n") print(scaled.mt) # Unscale the matrix unscaled.mt <- t(apply(scaled.mt, 1, function(r) r * attr(scaled.mt, 'scaled:scale') + attr(scaled.mt, 'scaled:center'))) # Print Unscaled matrix cat("Unscaled matrix:\n") print(unscaled.mt) |
chevron_right
filter_none
Output:
Original matrix:
[, 1] [, 2] [, 3] [, 4] [, 5]
[1, ] 1 5 9 13 17
[2, ] 2 6 10 14 18
[3, ] 3 7 11 15 19
[4, ] 4 8 12 16 20
Scaled matrix:
[, 1] [, 2] [, 3] [, 4] [, 5]
[1, ] -1.1618950 -1.1618950 -1.1618950 -1.1618950 -1.1618950
[2, ] -0.3872983 -0.3872983 -0.3872983 -0.3872983 -0.3872983
[3, ] 0.3872983 0.3872983 0.3872983 0.3872983 0.3872983
[4, ] 1.1618950 1.1618950 1.1618950 1.1618950 1.1618950
attr(, "scaled:center")
[1] 2.5 6.5 10.5 14.5 18.5
attr(, "scaled:scale")
[1] 1.290994 1.290994 1.290994 1.290994 1.290994
Unscaled matrix:
[, 1] [, 2] [, 3] [, 4] [, 5]
[1, ] 1 5 9 13 17
[2, ] 2 6 10 14 18
[3, ] 3 7 11 15 19
[4, ] 4 8 12 16 20
Using Mean and Standard Deviation
In this example, we’ll unscale the scaled matrix using mean and standard deviation of the original matrix.
# Create matrix a <- rnorm(5, 5, 2) b <- rnorm(5, 7, 5) mt <- cbind(a, b) # get center and scaling values m <- apply(df, 2, mean) s <- apply(df, 2, sd) # Print original matrix cat("Original matrix:\n") print(mt) # Scale the matrix scaled.mt <- scale(mt, center = m, scale = s) # Print Scaled matrix cat("Scaled matrix:\n") print(scaled.mt) # Unscale the matrix unscaled.mt <- t((t(scaled.mt) * s) + m) # Print Unscaled matrix cat("Unscaled matrix:\n") print(unscaled.mt) |
chevron_right
filter_none
Output:
Original matrix:
a b
[1, ] 5.552301 1.9865159
[2, ] 3.936486 17.5327829
[3, ] 5.379720 15.0981877
[4, ] 3.546333 0.5230305
[5, ] 5.043194 2.0930855
Scaled matrix:
a b
[1, ] 0.01543556 -2.062174
[2, ] -0.69057233 5.252016
[3, ] -0.05997146 4.106591
[4, ] -0.86104456 -2.750713
[5, ] -0.20701146 -2.012036
attr(, "scaled:center")
a b
5.516974 6.369655
attr(, "scaled:scale")
a b
2.288663 2.125494
Unscaled matrix:
a b
[1, ] 5.552301 1.9865159
[2, ] 3.936486 17.5327829
[3, ] 5.379720 15.0981877
[4, ] 3.546333 0.5230305
[5, ] 5.043194 2.0930855
attr(, "scaled:center")
a b
5.516974 6.369655
attr(, "scaled:scale")
a b
2.288663 2.125494
Recommended Posts:
- Check if the Object is a Matrix in R Programming - is.matrix() Function
- Convert an Object into a Matrix in R Programming - as.matrix() Function
- Convert a Data Frame into a Numeric Matrix in R Programming - data.matrix() Function
- Performing Logarithmic Computations in R Programming - log(), log10(), log1p(), and log2() Functions
- Array vs Matrix in R Programming
- Get or Set Dimensions of a Matrix in R Programming - dim() Function
- Getting the Determinant of the Matrix in R Programming - det() Function
- Getting a Matrix of number of rows in R Programming - row() Function
- Calculate Trace of a Matrix in R Programming - tr() Function
- Finding Inverse of a Matrix in R Programming - inv() Function
- Getting a Matrix of number of columns in R Programming - col() Function
- Get the position of the maximum element in each Row of a Matrix in R Programming - max.col() Function
- Create Matrix and Data Frame from Lists in R Programming
- Construct a Diagonal Matrix in R Programming - diag() Function
- Get Transpose of a Matrix or Data Frame in R Programming - t() Function
- Check if a Matrix is Symmetric or not in R Programming - isSymmetric() Function
- Calculate the Sum of Matrix or Array columns in R Programming - colSums() Function
- Create a Plot Matrix of Scatterplots in R Programming - pairs() Function
- Compute Choleski factorization of a Matrix in R Programming - chol() Function
- Calculate the cross-product of a Matrix in R Programming - crossprod() Function
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.
