Scilab Function
Last update : 5/9/2006

sis - the susceptible-infected-susceptible (SIS) model.

### Calling Sequence

  `[inf,infname] = sis(a,b,N,T,N0,P)`

### Parameters

- `a` : row vector of the numbers of the tail nodes of the graph (its size is the number of edges of the graph)
- `b` : row vector of the numbers of the head nodes of the graph (its size is the number of edges of the graph)
- `N` : the node number of the model
- `T` : the epidemic time step
- `N0` : the initial infected node
- `P` : the infected probability
- `inf` : row vector of the infected fraction of the graph(its size is the time step)
- `infname` : row vector of the infected node name

### Description

  sis calculates the infected fraction every time step for the SIS epidemic process.

### Examples

       Add here scilab instructions and comments

### See Also

`sirs` ,

### Authors

  Wubo