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Binary to decimal - Four ways to convert formats in Matlab

In this article we're going to present four variations of a binary to decimal conversion in Matlab; we're going to convert binary numbers (numbers with
only symbols '0' and '1') to decimal numbers (numbers with 10 different symbols, from '0' to '9').

First, I'm going to show you a video explaining the general ideas behind a base conversion. Later, I'm going to show you the ideas to make it happen in Matlab.

As you may know, a number expressed in decimal format (the common way to express a number, also called base 10) consists of additions of digits raised to the different powers of 10.

For example:

1528 (base 10) means 1 x 103 + 5 x 102 + 2 x 101 + 8 x 100

Following the same reasoning, a binary number (called to be in base 2) consists of additions of binary digits raised to the different powers of 2. For example:

1010 (base 2) means 1 x 23 + 0 x 102 + 1 x 101 + 0 x 20

1st. Method: using the bin2dec function.

The 'bin2dec' built-in function converts a binary number string to a decimal number.


bin_nr = '110101';
dec = bin2dec(bin_nr)

The result is dec = 53.

2nd. Method: using a for-loop.

In the event that we cannot use the bin2dec function for any reason, we have to elaborate an alternative. In this case, we just follow the logic explained above: every digit found in the input string is obtained with every iteration and it is converted into a real number (in this case the input is a string, not a number, that's why we use the instruction 'str2num').

bin_nr = '110101';
dec = 0;
for i = 1 : length(bin_nr)
    dec = dec + str2num(bin_nr(i)) * 2^(length(bin_nr) - i);


As expected, the result is also dec = 53.

3rd. Method: using a while-loop.

Now, we make a small change in the logic to work with a while-loop instead of a for-loop, just for a variation. The idea is the same, but we have to add an index to keep track of the appropriate power of the digit to be considered. This binary to decimal conversion also includes input from the user:

bin_nr = input('Enter your binary number: ', 's');
dec = 0;
i = 1;

while i < length(bin_nr) + 1
    dec = dec + str2num(bin_nr(i)) * 2^(length(bin_nr) - i);
    i = i + 1;


4rd. Method: using 'polyval'.

As seen in the articles about polynomials and curve fitting (see Table of Contents), the 'polyval' function with arguments (p, x) returns the value of a polynomial of degree n evaluated at x. The input argument p is a vector of length n+1 whose elements are the coefficients in descending powers of the polynomial to be evaluated. This is exactly what we need if the input is in vector form. In other words, the expected result is:

y = p1xn + p2xn-1 + ... + pnx + pn+1

And that's achieved this way:

bin_nr = [1 1 0 1 0 1];
dec = polyval(bin_nr, 2)

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