CODEWITHSUNDEEP
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Reputation: 2299

Converting to decimal in Matlab?

I am asking for an help to write a code doing the following in Matlab:

(1) I have a column vector A of dimension nx1 listing the n digits after the comma of a number B in base 4 between 0 and 1

What I mean by base 4 is explained here

Example

n=18
A=[1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2]' %representing B=0.121212121212121212

(2) I want to convert B to base 10 (decimal representation) and store the obtained decimal number C in a 1x1 matrix

Could you help me to understand how to do this?

Upvotes: 2

Views: 277

Answers (2)

Luis Mendo
Luis Mendo

Reputation: 112659

Here's a way:

C = base2dec(char(A(:).'+'0'), 4)*4^-numel(A);

This converts the digits to an integer in base 4 and then divides by the appropriate power of 4.

Take into account that C will be limited by double precision, so some decimals may be lost. If you want more precision you need to use symbolic variables.

Upvotes: 5

Matt
Matt

Reputation: 2802

I am assuming that you have the decimal place in there to slow that you want powers less than 1. Here is a brute force loop to do it.

C = 0;
for x = 1:n
    C = res + A(x) * 4 ^ (-x);
end
C = 0.399999999994179

Here is another way

exp = (-1 * (1:18))';
C = sum(A .* 4 .^ exp);
C = 0.399999999994179

Using your link as a guide let's look at the number in decimal of 15. This corresponds to the base 4 of 33. In this case A = [3 3] and exp = [1 0]. This results in:

A = [3 3];
exp = [1 0];
C = sum(A .* 4 .^ exp);
C = 15

Your link has a link explaining the basics of conversions.

Upvotes: 2

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