lin2log , log2lin (alias: dB)

Convert the elements of x to logarithmic values (e.g. dB) and vice versa.

Usage

lin2log(x {, ref {, fac}})

log2lin(x {, ref {, fac}})

x

a scalar, vector or matrix

ref

the reference value; must be a positive number (default=1)

fac

the factor; must be a positive number (default=20)

Result

The result r has the same type as x and contains the converted elements of x. The following conversion algorithms are used:

• lin2log: r_i,j = fac * log₁₀(x_i,j / ref)
• log2lin: r_i,j = ref * 10 ^ (x_i,j / fac)

Note: The function dB is an alias for log2lin and is implemented for compatibility with the expressions used in the NUM and INT command.

See also

log, exp, fft, cr2len

Example:

// #spe is a vector containing a complex spectrum
#aref := set '20e-6' // reference value: 20 micro Pascal
#logamp := eval lin2log(cr2len($#spe), $#aref) // the log. amplitude spectrum in dB

// apply 6dB attenuation to the signal stored in the vector #sig
$#sig := eval $#sig * db(6)

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