CODEWITHSUNDEEP
machine-learning
user3065339
user3065339

Reputation: 107

Sigmoid function different result from Matlab

How to code a sigmoid function in Java?, my output for hx = [0.51,0.51,0.51,0.51,0.51] is sigmoid =[1.6,1.6,1.6,1.6,1.6] and when I do it in Matlab the value of sigmoid is [ 0.6248 ,0.6248, 0.6248, 0.6248]:

public double[] sigmoidFunction() {
    int i;
    double[] sigmoid = new double[x_theta.length];
    for(i=0;i<x_theta.length; i++)
        sigmoid[i] = 1 / 1 + StrictMath.exp(-x_theta[i]);

    return sigmoid;
}

Upvotes: 2

Views: 440

Answers (1)

lejlot
lejlot

Reputation: 66775

You forgot about parenthesis:

sigmoid[i] = 1 / 1 + StrictMath.exp(-x_theta[i]);

is equivalent to

sigmoid[i] = (1 / 1) + StrictMath.exp(-x_theta[i]);

and so

sigmoid[i] = 1 + StrictMath.exp(-x_theta[i]);

while you seem to need

sigmoid[i] = 1 / ( 1 + StrictMath.exp(-x_theta[i]) );

Upvotes: 1

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