LOG10 LOG10 Base-10 Logarithm Function Usage Computes the log10 function for its argument. The general syntax for its use is y = log10(x) where x is an n-dimensional array of numerical type. Integer types are promoted to the double type prior to calculation of the log10 function. Output y is of the same size as the input x. For strictly positive, real inputs, the output type is the same as the input. For negative and complex arguments, the output is complex.