# Recursive binary to decimal function

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Rick on 12 Aug 2014
Answered: Geoff Hayes on 13 Aug 2014
Hello, I'm trying to write a function that will convert binary to decimal using recursion, but I am having difficulty getting the recursive part.
function y = Bin2dec(BA)
n = length(BA);
if n == 1
y = BA;
else
y = Bin2dec(BA(n-1));
end
Michael Haderlein on 12 Aug 2014
I have no idea what kind of conversion you want to do here, but maybe the error is that in case of the recursion (so, the if condition is false), you restart your function not with a limited array but only with one value. Most likely, you need to use
...
else
y = Bin2dec(BA(1:n-1));
end
...

Geoff Hayes on 13 Aug 2014
Rick - recursion is not really necessary to solve this problem. You can just iterate over each element in the input vector and sum the values according to
function y = myBin2dec(BA)
y = 0;
n = length(BA);
% move left to right in binary sequence
for k=n:-1:1
y = y + BA(n-k+1)*2^(k-1);
end
end
with
myBin2dec([0 0 0 1])
ans =
1
myBin2dec([1 0 0 0])
ans =
8
A recursive version could look like
function y = myBin2dec(BA)
y = 0;
n = length(BA);
if n>0
y = BA(1)*2^(n-1) + myBin2dec(BA(2:end));
end
end
and would return the same results as the previous example.

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