# Measure distance between current and previous state in terms of fish abundances

Source:`R/steady.R`

`distanceSSLogN.Rd`

Calculates the sum squared difference between log(N) in current and previous
state. This function can be used in `projectToSteady()`

to decide when
sufficient convergence to steady state has been achieved.

## Arguments

- params
MizerParams

- current
A named list with entries

`n`

,`n_pp`

and`n_other`

describing the current state- previous
A named list with entries

`n`

,`n_pp`

and`n_other`

describing the previous state

## Value

The sum of squares of the difference in the logs of the (nonzero)
fish abundances n:
`sum((log(current$n) - log(previous$n))^2)`

## See also

Other distance functions:
`distanceMaxRelRDI()`