sigmoid: Sigmoid function
In jakespiteri/chicagocrime: Organises and Explores the Chicago Crime Dataset

Sigmoid function, otherwise known as a logistic function

1	sigmoid(z)

z

input

The sigmoid (or logistic) function,

σ(z) = 1 / (1 + e^{-z})

is used in logistic regression to model probabilities, commonly the probability of predicting the positive class, i.e. p(y=1).

output value of the function

1
2
3

theta = c(1, 0.1)
X = matrix(rnorm(4), 2, 2)
sigmoid(X %*% theta)

jakespiteri/chicagocrime documentation built on Jan. 24, 2020, 1:26 a.m.

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