Conversion of a binary matrix to decimal matrix

Hello everyone,

I wonder if there is an easier way to convert a binary matrix to a decimal matrix?

For example: A = [1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0; 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0] (2x16 matrix) will be converted into B = [255 0; 15 240] (2x2 matrix). So, 8 bit binary numbers in the original matrix will be converted into decimal numbers. Or, in general, an Mx8N binary matrice will be converted into an MxN decimal matrice.

I know i can do it by using for loops and binaryVectorToDecimal or bi2de functions.

However, there might be a more easier way to do it by utilizing another built-in functions.

Thanks in advance,

Answer 1

[Stephen23]

The most efficient approach would probably be to avoid type conversion (e.g. to character) and to avoid BIN2DEC.

It is just as easy to do the whole thing with basic numeric operations:

A = [1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0;0,0,0,0,1,1,1,1,1,1,1,1,0,0,0,0]

A = 2×16

1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0

M = reshape(pow2(7:-1:0)*reshape(A.',8,[]),[],size(A,1)).'

M = 2×2

255 0 15 240

[Jan]

This is 5 times faster than the bin2dec approach.

To my surprise 2.^(7:-1:0) is faster than pow2(7:-1:0).

[Mehmet]

Thanks. This is so cool!

Answer 2

[Matt J]

A = [1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0;0,0,0,0,1,1,1,1,1,1,1,1,0,0,0,0];
e=kron(speye(2),2.^(7:-1:0)');

B = A*e

B = 2×2

255 0 15 240