How do I find maximum value of n so that 2^n is less than a value (ex, 500?)

I am working on making binary code using the power method. So what I am looking to do is make a function where I input a base 10 value and find the binary translation of this value. This will be done by calculating the largest value of 2^n that is smaller than or equall to the input. n will then be the number of rows in the matrix(only for this first instance). From there it will subtract this 2^n value from the input and repeat. The matrix will input going down from the largest n value to fill in the binary code, filling in 1s for when 2 to that n value exists and 0s for when it does not. These are based on calcualtions.

Anyway I am stuck on how to do this for finding max n values that are less than input value, any ideas? From here I feel comfortable creating loops to output binary code.

Answer 1

[Les Beckham]

I think you may be looking for log2. Documentation available here: https://www.mathworks.com/help/matlab/ref/log2.html

[Walter Roberson]

In particular, floor(log2(value))

However, you can get much more efficient by converting the number to integer datatype and using bitget(), or by converting to integer datatype and using dec2bin() and subtract '0' (the character for the digit zero) from the result.

[Ali Hamid]

So after we have the floor(log2(value)), is there a way to output the remainder?

[Walter Roberson]

closest_power2 = 2.^floor(log2(value));
value = value - closest_power2.