Octal to decimal - Two methods in Matlab

Basics

Similarly, the decimal system (base 10) has ten symbols, '0' to '9' and the binary system (base 2) has only two symbols, '0' and '1'.

Table equivalents: decimal, octal and binary numbers
 

You can see that from 0 to 7 a number in octal is exactly the same as it is in decimal, but what if you need to go beyond 7?

Video

Here's a video that explains you the concepts behind the numerical equivalencies in different systems. After the video, we show you how to code that in Matlab. 

Solution 1. Conversion from Octal to Decimal using the obvious way in Matlab

We can go from octal to decimal by using the function base2dec, which converts a base-N number string to a decimal number. Its syntax is  

base2dec('string', base)

For example, base2dec('100', 8) produces a 64 in decimal and 
           base2dec('1352', 8) produces a 746.

It’s important to remember that octal numbers are treated as strings. 

Solution 2. Conversion using a different approach 

This is the idea that is shown on the video. 

clear, clc,  format compact 

% Here we keep our octal number
o = '317' 

% The decimal equivalent starts being 0
d = 0;
% Let's flip the octal symbol to align with the
% exponents that follow
f = fliplr(o);
% Now we create the appropriate exponent
for p = 0 : length(o) - 1
    % This is the necessary multiplication and addition
    % to achieve our idea, digit-by-digit
    d = d + str2num(f(p+1)) * 8^p;
end
% Now, we just display the result
d

If you run the code above, you'll get this result on screen (edited for clarity).