log,Expression-method {CVXR} R Documentation

## 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)

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
```

[Package CVXR version 1.0-10 Index]