# SSlogis

##### Self-Starting Nls Logistic Model

This `selfStart`

model evaluates the logistic
function and its gradient. It has an `initial`

attribute that
creates initial estimates of the parameters `Asym`

,
`xmid`

, and `scal`

.

- Keywords
- models

##### Usage

`SSlogis(input, Asym, xmid, scal)`

##### Arguments

- input
- a numeric vector of values at which to evaluate the model.
- Asym
- a numeric parameter representing the asymptote.
- xmid
- a numeric parameter representing the
`x`

value at the inflection point of the curve. The value of`SSlogis`

will be`Asym/2`

at`xmid`

. - scal
- a numeric scale parameter on the
`input`

axis.

##### Value

a numeric vector of the same length as `input`

. It is the value of
the expression `Asym/(1+exp((xmid-input)/scal))`

. If all of
the arguments `Asym`

, `xmid`

, and `scal`

are
names of objects the gradient matrix with respect to these names is attached as
an attribute named `gradient`

.

##### See Also

##### Examples

`library(stats)`

```
```

*Documentation reproduced from package stats, version 3.3.3, License: Part of R 3.3.3*

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