logarithm of base other than e,10 and 2

how do i find logarithms having base other than e, 10 and 2.

Answer 1

[James Tursa]

logB(X) = logA(X) / logA(B)

You can pick A to be one of the built in functions, like log or log2 or log10. E.g.,

log3(9) = log(9) / log(3) , or
log3(9) = log10(9) / log10(3) , etc.

[Stephen23]

Note that for many MATLAB versions log10 itself called log2 internally... so you might as well skip the intermediate log10 and just call log2 directly (it is probably more accurate as well).

Answer 2

[Tsegts]

how to write that base 3 log

[Walter Roberson]

log(x)./log(3)

Answer 3

[Chris Lucero]

y = logb(magic(3),[1 2 3; 4 5 6; 7 8 9]);

[Walter Roberson]

logb appears to refer to the File Exchange contribution https://www.mathworks.com/matlabcentral/fileexchange/14866-logb

Answer 4

[Walter Roberson]

if you really get desparate:

arrayfun(@(V) feval(symengine,'log', B, V), A)

and you might want to double() the result. Note that for this to work, B must be a positive real number, whereas in Jame's solution of log(A)/log(B) then B does not need to be positive and does not need to be real-valued.

Answer 5

[lina al noaimi]

how do we convert from base 9 to base 12 in matlab

can you give me an example on it

[Walter Roberson]

If you mean numeric base, in the same sense that Hexadecimal representation is base 16 number system, then use base2dec and dec2base.

If you mean log base then log12(x) = log9(x).^(9/12)