01204472/perceptron algorithm

หน้านี้เป็นตัวอย่างประกอบวิชา 01204472

Perceptron algorithm เป็นอัลกอริทึมสำหรับเรียน linear threshold function จากตัวอย่าง (อ่านเพิ่มเติมได้จาก บทความในวิกิพีเดีย)

Linear threshold function $f:R^{n}\rightarrow \{+1,-1\}$ จะถูกระบุด้วยพารามิเตอร์ $w$ มีนิยามดังด้านล่างนี้

$f(x)=\left\{{\begin{array}{ll}1&{\mbox{if}}\;\;w^{T}x>0,\\-1&{\mbox{otherwise}}\end{array}}\right.$

มีขั้นตอนการทำงานดังนี้

1. กำหนดให้เวกเตอร์ $w_{1}=0$ ให้ $t=1$
2. เมื่อได้อินพุตตัวอย่าง $x$, ทำนายว่า +1 iff $w_{t}^{T}x>0$
3. ถ้าตอบผิด ปรับค่าดังนี้
   • ถ้าตอบผิดในกรณีที่เฉลยเป็น +1 ให้ $w_{t+1}\leftarrow w_{t}+x$
   • ถ้าตอบผิดในกรณีที่เฉลยเป็น -1 ให้ $w_{t+1}\leftarrow w_{t}-x$
   • จากนั้นให้ $t\leftarrow t+1$

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