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# Tips:Calculate logarithm of any base

data show; val = 55; b2 = log2(val); v2 = log(val) / log(2); put b2= ; put v2=; run;

SAS supports only 3 bases for the log function, namely, {2, 10, exp(1)}, corresponding to functions log2(), log10(), and log(), respectively.

Sometimes, we need to calculate log value of any positive base number, just as in Excel or some other programming environment, we have function like log(Val, Base). It is not hard to do so by noting that we can calculate logarithms with other base values by dividing the result of the log() function with log(base), where log() is the natural logarithm function.

Therefore, log(Value, Base)=log(Value)/log(Base). This can be shown in this short DATA step to the right.