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MATLAB: how to normalize/denormalize a vector to range [-1;1]
Hi, just started using Matlab and I would like to know how to rescale the data in a matrix. I have a matrix of N rows by M columns and want to rescale the data in the columns to be between -1 and 1.
Each column contains values that vary in scale from say 0 - 10,000 to some that are between 0 and 1, the reason I want to normalise to between -1 and 1 as these values will be used in a Neural Network as input values for a transform function that is sine based.
Neither of the previous answers are correct. This is what you need to do:
[rows,~]=size(A);%# A is your matrix
colMax=max(abs(A),[],1);%# take max absolute value to account for negative numbers
normalizedA=A./repmat(colMax,rows,1);
The matrix normalizedA will have values between -1 and 1.
Example:
A=randn(4)
A =
-1.0689 0.3252 -0.1022 -0.8649
-0.8095 -0.7549 -0.2414 -0.0301
-2.9443 1.3703 0.3192 -0.1649
1.4384 -1.7115 0.3129 0.6277
normalizedA =
-0.3630 0.1900 -0.3203 -1.0000
-0.2749 -0.4411 -0.7564 -0.0347
-1.0000 0.8006 1.0000 -0.1906
0.4885 -1.0000 0.9801 0.7258
A simple solution would use simple logic. Assuming that you mean to scale EACH column independently, do this:
- Subtract off the column minimum for each column.
- Scale the column maximum to be 2.
- Subtract 1.
Clearly this will result in the min for each column to be -1, the max will be 1. Code to do so is simple enough.
A = randn(5,4) % some random example data
A =
0.70127 0.20378 0.4085 0.83125
0.64984 -0.90414 0.67386 1.2022
1.6843 -1.6584 -0.31735 -1.8981
-1.3898 -0.89092 -0.23122 -1.2075
0.72904 -0.095776 0.67517 0.28613
Now, perform the steps above to A.
A = bsxfun(@minus,A,min(A,[],1));
A = bsxfun(@times,A,2./max(A,[],1));
A = A - 1
A =
0.36043 1 0.46264 0.76071
0.32697 -0.18989 0.99735 1
1 -1 -1 -1
-1 -0.1757 -0.82646 -0.55446
0.3785 0.67828 1 0.40905
[m, n] = size(normalizedMatrix)
normalizedMatrix*2-ones(m,n)
来源：https://stackoverflow.com/questions/5641232/matlab-rescale-matrix-data-to-1-to-1