I made a logistic regression model using glm in R. I have two independent variables. How can I plot the decision boundary of my model in the scatter plot of the two variables. For example, how can I plot a figure like:

http://onlinecourses.science.psu.edu/stat557/node/55Thanks.

**Answer**

```
set.seed(1234)
x1 <- rnorm(20, 1, 2)
x2 <- rnorm(20)
y <- sign(-1 - 2 * x1 + 4 * x2 )
y[ y == -1] <- 0
df <- cbind.data.frame( y, x1, x2)
mdl <- glm( y ~ . , data = df , family=binomial)
slope <- coef(mdl)[2]/(-coef(mdl)[3])
intercept <- coef(mdl)[1]/(-coef(mdl)[3])
library(lattice)
xyplot( x2 ~ x1 , data = df, groups = y,
panel=function(...){
panel.xyplot(...)
panel.abline(intercept , slope)
panel.grid(...)
})
```

I must remark that perfect separation occurs here, therefore the `glm`

function gives you a warning. But that is not important here as the purpose is to illustrate how to draw the linear boundary and the observations colored according to their covariates.

**Attribution***Source : Link , Question Author : user2755 , Answer Author : Community*