log,Expression-method {CVXR}

Logarithms

Description

The elementwise logarithm. log computes the logarithm, by default the natural logarithm, log10 computes the common (i.e., base 10) logarithm, and log2 computes the binary (i.e., base 2) logarithms. The general form log(x, base) computes logarithms with base base. log1p computes elementwise the function \log(1+x).

Usage

## S4 method for signature 'Expression'
log(x, base = base::exp(1))

## S4 method for signature 'Expression'
log10(x)

## S4 method for signature 'Expression'
log2(x)

## S4 method for signature 'Expression'
log1p(x)

Arguments

x

An Expression.

base

(Optional) A positive number that is the base with respect to which the logarithm is computed. Defaults to e.

Value

An Expression representing the exponentiated input.

Examples

# Log in objective
x <- Variable(2)
obj <- Maximize(sum(log(x)))
constr <- list(x <= matrix(c(1, exp(1))))
prob <- Problem(obj, constr)
result <- solve(prob)
result$value
result$getValue(x)

# Log in constraint
obj <- Minimize(sum(x))
constr <- list(log2(x) >= 0, x <= matrix(c(1,1)))
prob <- Problem(obj, constr)
result <- solve(prob)
result$value
result$getValue(x)

# Index into log
obj <- Maximize(log10(x)[2])
constr <- list(x <= matrix(c(1, exp(1))))
prob <- Problem(obj, constr)
result <- solve(prob)
result$value

# Scalar log
obj <- Maximize(log1p(x[2]))
constr <- list(x <= matrix(c(1, exp(1))))
prob <- Problem(obj, constr)
result <- solve(prob)
result$value